2.0版，448行

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <memory>
#include <stdexcept>
#include <type_traits>
#include <utility>
#include <tuple>
#include <array>
#include <deque>
#include <list>
#include <forward_list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <stack>
#include <queue>
#include <iterator>
#include <numeric>
#include <limits>
#include <cmath>
#include <cctype>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <climits>
#include <cwchar>
#include <cwctype>
#include <exception>
#include <locale>
#include <codecvt>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <istream>
#include <ostream>
#include <sstream>
#include <streambuf>
#include <complex>
#include <valarray>
#include <bitset>
#include <regex>
#include <random>
#include <chrono>
#include <initializer_list>
#include <system_error>
#include <future>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <atomic>
#include <cfenv>
#include <cinttypes>
#include <cstdint>
#include <cuchar>
#include <new>
#include <typeinfo>
#include <ratio>
#include <scoped_allocator>
#include <ciso646>
#include <clocale>
#include <cstdarg>
#include <cstdbool>
#include <cstddef>
#include <csetjmp>
#include <csignal>
#include <cfloat>
#include <cerrno>

// ==================== 层1：编译时计算 ====================
namespace CompileTimeMath {
    template<int N>
    struct Fibonacci {
        static constexpr int value = Fibonacci<N-1>::value + Fibonacci<N-2>::value;
    };
    
    template<> struct Fibonacci<0> { static constexpr int value = 0; };
    template<> struct Fibonacci<1> { static constexpr int value = 1; };
    
    template<int A, int B>
    struct StaticAdd {
        static constexpr int value = A + B;
    };
}

// ==================== 层2：异常系统 ====================
class ArithmeticException : public std::exception {
    std::string msg;
public:
    ArithmeticException(const std::string& m) : msg(m) {}
    const char* what() const noexcept override { return msg.c_str(); }
};

// ==================== 层3：抽象接口 ====================
class IAdder {
public:
    virtual ~IAdder() = default;
    virtual std::string add(const std::string& a, const std::string& b) const = 0;
    virtual std::string getName() const = 0;
};

// ==================== 层4：具体实现 ====================
class SimpleAdder : public IAdder {
public:
    std::string add(const std::string& a, const std::string& b) const override {
        std::string result;
        int carry = 0;
        int i = a.size() - 1;
        int j = b.size() - 1;
        
        while (i >= 0 || j >= 0 || carry) {
            int sum = carry;
            if (i >= 0) sum += a[i--] - '0';
            if (j >= 0) sum += b[j--] - '0';
            carry = sum / 10;
            result.push_back('0' + (sum % 10));
        }
        
        std::reverse(result.begin(), result.end());
        if (result.empty()) return "0";
        
        size_t pos = result.find_first_not_of('0');
        return pos == std::string::npos ? "0" : result.substr(pos);
    }
    
    std::string getName() const override { return "SimpleAdder"; }
};

class FastAdder : public IAdder {
public:
    std::string add(const std::string& a, const std::string& b) const override {
        if (a.size() < b.size()) return add(b, a);
        
        std::string result = a;
        int carry = 0;
        int i = a.size() - 1;
        int j = b.size() - 1;
        
        while (i >= 0) {
            int digit_a = result[i] - '0';
            int digit_b = j >= 0 ? b[j--] - '0' : 0;
            int sum = digit_a + digit_b + carry;
            carry = sum / 10;
            result[i] = '0' + (sum % 10);
            i--;
        }
        
        if (carry) result = "1" + result;
        return result;
    }
    
    std::string getName() const override { return "FastAdder"; }
};

// ==================== 层5：装饰器 ====================
class AdderDecorator : public IAdder {
protected:
    std::unique_ptr<IAdder> wrapped;
public:
    AdderDecorator(std::unique_ptr<IAdder> adder) : wrapped(std::move(adder)) {}
    
    std::string add(const std::string& a, const std::string& b) const override {
        return wrapped->add(a, b);
    }
    
    std::string getName() const override {
        return wrapped->getName();
    }
};

class ValidatingAdder : public AdderDecorator {
public:
    using AdderDecorator::AdderDecorator;
    
    std::string add(const std::string& a, const std::string& b) const override {
        // 输入验证
        for (char c : a) if (!isdigit(c)) throw ArithmeticException("Invalid digit in a");
        for (char c : b) if (!isdigit(c)) throw ArithmeticException("Invalid digit in b");
        
        // 计算
        std::string result = wrapped->add(a, b);
        
        // 结果验证
        if (!result.empty() && result[0] == '0' && result.size() > 1) {
            throw ArithmeticException("Invalid result format");
        }
        
        return result;
    }
};

class TimingAdder : public AdderDecorator {
public:
    using AdderDecorator::AdderDecorator;
    
    std::string add(const std::string& a, const std::string& b) const override {
        auto start = std::chrono::high_resolution_clock::now();
        std::string result = wrapped->add(a, b);
        auto end = std::chrono::high_resolution_clock::now();
        
        auto duration = std::chrono::duration_cast<std::chrono::microseconds>(end - start);
        // 可以记录时间，这里不输出以免影响OJ
        (void)duration; // 避免未使用警告
        
        return result;
    }
};

// ==================== 层6：工厂 ====================
class AdderFactory {
public:
    enum AdderType { SIMPLE, FAST, VALIDATED, TIMING };
    
    static std::unique_ptr<IAdder> create(AdderType type) {
        switch (type) {
            case SIMPLE: return std::make_unique<SimpleAdder>();
            case FAST: return std::make_unique<FastAdder>();
            case VALIDATED: 
                return std::make_unique<ValidatingAdder>(std::make_unique<SimpleAdder>());
            case TIMING:
                return std::make_unique<TimingAdder>(
                    std::make_unique<ValidatingAdder>(std::make_unique<FastAdder>()));
            default: return std::make_unique<SimpleAdder>();
        }
    }
};

// ==================== 层7：输入处理器 ====================
class InputProcessor {
private:
    std::string trim(const std::string& s) {
        auto start = s.find_first_not_of(" \t\n\r");
        auto end = s.find_last_not_of(" \t\n\r");
        if (start == std::string::npos) return "";
        return s.substr(start, end - start + 1);
    }
    
    bool isValidNumber(const std::string& s) {
        if (s.empty()) return false;
        for (char c : s) if (!isdigit(c)) return false;
        
        try {
            // 检查是否在范围内
            if (s.size() > 10) return false; // 超过int范围
            long long val = std::stoll(s);
            return val >= 0 && val <= 1000000000;
        } catch (...) {
            return false;
        }
    }
    
public:
    std::pair<std::string, std::string> parseInput() {
        std::string line;
        if (!std::getline(std::cin, line)) {
            throw ArithmeticException("无法读取输入");
        }
        
        std::istringstream iss(line);
        std::vector<std::string> tokens;
        std::string token;
        
        while (iss >> token) {
            tokens.push_back(token);
        }
        
        if (tokens.size() != 2) {
            throw ArithmeticException("需要恰好两个数字");
        }
        
        tokens[0] = trim(tokens[0]);
        tokens[1] = trim(tokens[1]);
        
        if (!isValidNumber(tokens[0]) || !isValidNumber(tokens[1])) {
            throw ArithmeticException("无效的数字格式或超出范围");
        }
        
        return {tokens[0], tokens[1]};
    }
};

// ==================== 层8：验证器 ====================
class ResultValidator {
public:
    static bool validateAddition(const std::string& a, const std::string& b, const std::string& result) {
        // 方法1：使用字符串加法验证
        SimpleAdder simple;
        std::string expected = simple.add(a, b);
        
        // 方法2：如果数字小，使用整数验证
        try {
            if (a.size() <= 9 && b.size() <= 9) {
                long long val_a = std::stoll(a);
                long long val_b = std::stoll(b);
                long long val_result = std::stoll(result);
                if (val_a + val_b != val_result) return false;
            }
        } catch (...) {
            // 忽略转换异常，使用字符串验证
        }
        
        return expected == result;
    }
};

// ==================== 层9：计算引擎 ====================
class CalculationEngine {
private:
    std::unique_ptr<IAdder> adder;
    InputProcessor inputProcessor;
    int computationCount;
    
public:
    CalculationEngine() : computationCount(0) {
        // 根据编译时计算结果选择算法
        constexpr int fib10 = CompileTimeMath::Fibonacci<10>::value;
        constexpr int staticSum = CompileTimeMath::StaticAdd<1, 1>::value;
        
        // 使用编译时信息选择算法
        if constexpr (fib10 > 50 && staticSum == 2) {
            adder = AdderFactory::create(AdderFactory::TIMING);
        } else {
            adder = AdderFactory::create(AdderFactory::VALIDATED);
        }
    }
    
    std::string execute() {
        try {
            auto [a, b] = inputProcessor.parseInput();
            
            // 记录计算
            computationCount++;
            
            // 执行计算
            std::string result = adder->add(a, b);
            
            // 验证结果
            if (!ResultValidator::validateAddition(a, b, result)) {
                throw ArithmeticException("结果验证失败");
            }
            
            // 使用编译时计算进行最终检查
            constexpr int check = CompileTimeMath::StaticAdd<0, 0>::value;
            static_assert(check == 0, "编译时验证失败");
            
            return result;
            
        } catch (const std::exception& e) {
            // 回退方案
            std::cerr << "错误: " << e.what() << "，使用简单方法重试..." << std::endl;
            return fallbackCalculation();
        }
    }
    
private:
    std::string fallbackCalculation() {
        std::string line;
        std::getline(std::cin, line);
        std::istringstream iss(line);
        long long a, b;
        
        if (iss >> a >> b) {
            if (a < 0 || a > 1000000000 || b < 0 || b > 1000000000) {
                throw ArithmeticException("数字超出范围");
            }
            return std::to_string(a + b);
        }
        
        throw ArithmeticException("无法恢复的输入错误");
    }
};

// ==================== 层10：主程序 ====================
int main() {
    try {
        // 初始化引擎
        CalculationEngine engine;
        
        // 执行计算
        std::string result = engine.execute();
        
        // 输出结果
        std::cout << result << std::endl;
        
        // 使用复杂的返回逻辑
        int returnCode = 0;
        
        // 使用编译时验证确保正确性
        static_assert(CompileTimeMath::StaticAdd<2, 2>::value == 4, "数学基础错误");
        
        // 使用条件编译
        #ifdef __cplusplus
            if (__cplusplus >= 201103L) {
                returnCode = EXIT_SUCCESS;
            } else {
                returnCode = 0;
            }
        #else
            returnCode = 0;
        #endif
        
        // 最终返回
        asm volatile ("" : : "r"(returnCode)); // 阻止优化
        
        if (returnCode == EXIT_SUCCESS || returnCode == 0) {
            return returnCode;
        }
        
        // 理论上不会到达这里
        return 1;
        
    } catch (const std::exception& e) {
        std::cerr << "致命错误: " << e.what() << std::endl;
        
        // 终极回退
        std::string line;
        if (std::getline(std::cin, line)) {
            std::istringstream iss(line);
            int a, b;
            if (iss >> a >> b) {
                std::cout << (a + b) << std::endl;
                return 0;
            }
        }
        
        return 1;
    }
}

// ==================== 层11：静态断言 ====================
namespace StaticVerification {
    // 验证编译时计算
    static_assert(CompileTimeMath::Fibonacci<0>::value == 0, "F(0)错误");
    static_assert(CompileTimeMath::Fibonacci<1>::value == 1, "F(1)错误");
    static_assert(CompileTimeMath::Fibonacci<5>::value == 5, "F(5)错误");
    static_assert(CompileTimeMath::Fibonacci<10>::value == 55, "F(10)错误");
    
    // 验证加法
    static_assert(CompileTimeMath::StaticAdd<0, 0>::value == 0, "0+0错误");
    static_assert(CompileTimeMath::StaticAdd<1, 1>::value == 2, "1+1错误");
    static_assert(CompileTimeMath::StaticAdd<100, 200>::value == 300, "100+200错误");
    static_assert(CompileTimeMath::StaticAdd<999999999, 1>::value == 1000000000, "边界测试错误");
}