题解在此

#include <iostream>
#include <cmath>
using namespace std;
int main(){
    int k;
    string s;
    cin>>k>>s;
    long long sum=0,cnt=s.size()-1;
    for (int i=0;i<s.size();i++){
        if (s[i]>='A'&&s[i]<='Z'){
            sum+=int(s[i]-55)*pow(k,cnt);
        }else if (s[i]>='0'&&s[i]<='9'){
            sum+=(s[i]-'0')*pow(k,cnt);
        }
        cnt--;
    }
    cout<<sum;
    return 0;
}