gcd c++
#include<bits/stdc++.h>
using namespace std;
long long UCLN(long long a,long long b)
{
long long r;
while (b!=0)
{
r=a%b;
a=b;
b=r;
}
return a;
}
int main()
{
long long a, b;
cout<< "enter: ";
cin>> a;
cout<< "enter: ";
cin >>b;
cout<<UCLN(a,b)<<endl;
return 0;
}