#include <iostream>
using namespace std;

int main()
{
	unsigned long long int n, a, answer;
	cin >> n >> a;
	if (a > 1)
	{
		answer = n*a;
		for(unsigned long long int i = n-1; i > 0; --i)
			answer = (answer+i)*a;
	}
	else
		answer = n*(n+1)/2;
	cout << answer;
	return 0;
}