辗转相除法

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
// 辗转相除法
// gcd(a, b) = gcd(b, a % b)
int gcd(int a, int b){
    return b ? gcd(b, a % b) : a;
}
int main(){
    int a, b;
    cin >> a >> b;
    cout << gcd(a, b) << endl;
    return 0;
}