#include<iostream>
#include<cstdio>

using namespace std;

int main()
{
    int A , N;

    cin >> A;

    while(cin >> N , N <= 0); //先读入N，再判断N是否小于等于0 如果N小于等于0 就继续循环

    int sum = 0;

    for(int i = 0; i < N ; i++)
    {

        sum += A + i; 

    }


    cout << sum << endl;


    return 0;
}