// GCD by repeated subtraction.

fn gcd(mut a: i32, mut b: i32) -> i32 {
    while a != b {
        if a > b { a -= b; } else { b -= a; }
    }
    a
}

fn main() {
    for p in &[(48, 18), (100, 75), (17, 5), (12, 12)] {
        println!("gcd({}, {}) = {}", p.0, p.1, gcd(p.0, p.1));
    }
}