#include <iostream>

using namespace std;


int main(){
	long long v, t;


	while(cin >> v >> t){

		long long t2 = t * 2;

		if(t2 == 0 || v == 0){
			cout << 0 << endl;

		} else {
			long long a = v/t2;
			long long displacement = v * t2 + (1/2 * a * t2 * t2); 
			cout << displacement << endl;

		}

		

	}
	

	return 0;
}