正经题解

#include<bits/stdc++.h>
using namespace std;
void ZS_n_D(int q,string s){ // N进制转十进制(整数) 
    vector<int> ve;
    for(int i = 0;i < s.size();i++){
        if(s[i] >= '0' && s[i] <= '9') ve.push_back(s[i] - '0');
        else ve.push_back(s[i] - 55);
    }
    reverse(ve.begin(),ve.end());
    long long ans = 0,power = 0;
    for(int i = 0;i < ve.size();i++){
        ans += ve[i] * pow(q,power);
        power++;
    }
    cout << ans;
    return ;
}
int main(){
    int q;
    string s;
    cin >> q >> s;
    ZS_n_D(q,s);
	return 0;
}