为什么只有#8WA啊！！！（疯掉）

#include <iostream>
using namespace std;

string code;
int turtle;

void run(int start, int end) {
	if (start >= end)
		return ;
	int val = 0, i;
	switch (code[start]) {
		case 'F'://前进
			i = start + 3;
			for (; code[i] - '0' >= 0 && code[i] - '0' < 9; i++) {
				val *= 10;
				val += code[i] - '0';
			}
			turtle += val;
			run(i + 1, end);
			break;

		case 'B'://后退
			i = start + 3;
			for (; code[i] - '0' >= 0 && code[i] - '0' < 9; i++) {
				val *= 10;
				val += code[i] - '0';
			}
			turtle -= val;
			run(i + 1, end);
			break;

		case 'R'://重复
			i = start + 7;
			for (; code[i] - '0' >= 0 && code[i] - '0' < 9; i++) {
				val *= 10;
				val += code[i] - '0';
			}
			int kuohaos = 1, j = i + 1;
			while (kuohaos) {
				if (code[j] == '[') {
					kuohaos++;
				}
				if (code[j] == ']') {
					kuohaos--;
				}
				j++;
			}
			for (int _ = 0; _ < val; _++) {
				run(i + 1, j - 1);
			}
			run(j + 1, end);
			break;

	}
}

int main() {
	getline(cin, code);
	run(0, code.size() - 1);
	cout << ((turtle > 0) ? turtle : -turtle);
	return 0;
}