题解

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int x, arr[105]; 
string str;
int a(char c) {
    if( '0' <= c && c <= '9'){
    	 return c - '0';
	}
    return c - 'A' + 10;
}
int main() {
	ll sum = 0,c = 1;
    cin >> x >> str;
    int l = str.size();
    for(int i = l - 1;i >= 0;i --)
        arr[l - 1 - i] = a(str[i]);
    for(int i = 0;i < l + 1;i ++){
        sum += c * arr[i];
        c *= x;
    }
    cout << sum;
    return 0;
}