#include <stdio.h>

int mcd(int a, int b) {
    if (a == 0) {
        return b;
    }

    if (a > b) {
        return mcd(a % b, b);
    } else {
        return mcd(b % a, a);
    }
}

int main()
{
    int a, b, res;
    if (scanf("%d %d", &a, &b) != 2) {
        puts("Error, invalid input!");
        return 1;
    }

    if (a < 0 || b < 0) {
        puts("Error, you must insert two positive integers!");
        return 1;
    }

    res = mcd(a, b);
    printf("MCD = %d\n", res);

    return 0;
}