Bases Multiplication

    1#include <bits/stdc++.h>
    2 
    3using namespace std;
    4string convert_base(long long num, long long base){
    5    vector<int> remainder;
    6    if(num == 0){
    7        return "0";
    8    }
    9    while(num != 0){
    10        remainder.push_back(num % base);
    11        num /= base;
    12    }
    13    string temp;
    14    for(int i = remainder.size() -1; i >= 0; i--){
    15        temp += (char) ('0' + remainder[i]);
    16    }
    17    return temp;
    18}
    19long long p(long long base, long long exp){
    20    if(exp == 0) return 1;
    21    long long temp = p(base, exp / 2);
    22    if(exp & 1){
    23        return temp * temp * base;
    24    } else {
    25        return temp * temp;
    26    }
    27}
    28int main(){
    29    ios::sync_with_stdio(0);
    30    cin.tie(0);
    31    int tt = 5;
    32    while(tt--){
    33        long long n1, b1, n2, b2, tar;
    34        cin >> n1 >> b1 >> n2 >> b2 >> tar;
    35        string s1 = to_string(n1), s2 = to_string(n2);
    36        long long a1 = 0, a2 = 0;
    37        int digit = 0;
    38        for(int i = s1.size() - 1; i >= 0; i--){
    39            long long pow = p(b1, digit);
    40            a1 += (s1[i] - '0') * pow;
    41            digit++;
    42        }
    43        digit = 0;
    44        for(int i = s2.size() - 1; i >= 0; i--){
    45            long long pow = p(b2, digit);
    46            a2 += (s2[i] - '0') * pow;
    47            digit++;
    48        }
    49        long long ans = a1 * a2;
    50        string out = convert_base(ans, tar);
    51        cout << out << '\n';
    52    }
    53    return 0;
    54}