#include <iostream>
#include <vector>
using namespace std;

vector<int> res;

int main() {
    long num1, num2, sum, target;//A+B可能超出int,最大2^32-2,long即可
    while (cin >> target >> num1 >> num2) {
        // if(target==0)   break;
        sum = num1 + num2;
        while (sum != 0) {//除基取余法,低位至高位
            res.push_back(sum % target);
            sum /= target;
        }
        for (int i = res.size() - 1; i > -1; i--)
            cout << res[i];
        if (res.size() == 0) cout << 0;
        res.clear();
        cout << endl;
    }
}

进制转换,可以考虑类似十转二的除基取余。