Extended GCD

#include <bits/stdc++.h>

long long x = 1, y, r, s = 1, s1, r1;

int main()
{
    long a, b, a0, b0;
    long long c;
    std::cin >> a >> b >> c;
    a0 = a;     b0 = b;
    while(b!=0)
    {
        long long c1 = a%b;
        long long q = a/b;
        a = b;
        b = c1;

        r1 = r;
        s1 = s;
        r = x - q * r;
        s = y - q * s;
        x = r1;
        y = s1;
    }
    if (c == a0 *x + b0*y)    std::cout << x<< " " <<  y;
    else std::cout <<"NIE";
    return 0;
}