#include <iostream>

using namespace std;

int gcd(int m, int n);

int gcd(int m, int n)
{
    if (m <= 0 || n <= 0)
        return 0; // invalid

    if (m % n == 0)
        return n;
    else
        return gcd(n, m%n);
}

int main(int argc, const char *argv[])
{
    cout << "gcd(24,16) = " << gcd(24,16) << endl;
    cout << "gcd(255, 25) = " << gcd(255,25) << endl;
    return 0;
}