oi-wiki

#include <iostream>
#include <cmath>

using namespace std;

using ll = long long;

ll fxxk(ll a, ll b) {
	return b == 0 ? a : fxxk(b, a % b);
}

int main() {
	ll a, b;
	cin >> a >> b;
	cout << fxxk(a, b) << '\n';
	return 0;
}