H(x) = R(x) mod n (C++ programma)

#include <iostream>
using namespace std;

int rxmodn(int num, int& sum) {

    int second = num % 100;
    int first = (num - second)/100;

    if(num == 0){
        return 0;
    }else {
        sum = sum + second;
    }

    return rxmodn(first, sum);
}

int main() {

    int sum = 0, num = 87835423;
    rxmodn(num, sum);
    cout << sum;
    return 0;
}