Great Common Divisor

#include <iostream>

using namespace std;

int gcd1(int m, int n)
{
    for (int div = m > n ? n : m; div >= 1; div--) {
        if (m % div == 0 && n % div == 0) {
            return div;
        }
    }

    return 0;
}

int gcd2(int m, int n)
{
    if (n == 0) {
        return m;
    } else {
        return gcd2(n, m % n);
    }
}

int main()
{
    int m = 18;
    int n = 12;
    cout << m << " " << n << " " << gcd1(m, n) << " " << gcd2(m, n) << endl;

    m = 17, n = 18;

    cout << m << " " << n << " " << gcd1(m, n) << " " << gcd2(m, n) << endl;
}