GCD

 #include <iostream>

 using namespace std;

 void gcd(int n1,int n2){

    int gcd;

   while(n1>0&&n2>0){

    if(n1>n2)n1=n1%n2;

    else n2=n2%n1;

   }

   if(n1==0)gcd=n2;

   gcd=n1;

   cout<<gcd<<endl;

 }

 int main() {

 //Write your C++ code here

 cout << "Hello, World!" << endl;

 gcd(6,12);

 return 0;

 }