#include <stdio.h>

int gcd(int x, int y);

int main() {
    printf("gcd = %d\n", gcd(12, 15));

    return 0;
}

int gcd(int x, int y){
    int min;
    int ret = 0;
    
    if(x > y){
        min = y;
    } else {
        min = x;
    }
    
    for(int i = 1; i<=min; i++){
        if((x%i ==0) && (y%i == 0)){
            ret = i;
        }
    }
    
    return ret;
}