答案

#include <bits/stdc++.h>
using namespace std; 
int f(int a,int b)
{
	if(a%b==0) return b;
	else return f(b,a%b);
}
int main()
{
	int a,b;
	cin>>a>>b; 
	cout<<f(a,b);
	return 0;
}