#include <iostream.h>
 int sums(int n,int i){ int sum=0;
	 for (i = 1; i <= n; ++i) {
		  sum += i;
	 } return sum;}


int main()
{
	 int x,y;
cin>>x;
cin>>y;
int sum=sums(x,y);

	 cout << "Sum = " << sum;

}