Uri 1149

#include <bits/stdc++.h>

using namespace std;

int main() {
    int a, n = 0, sum = 0;
    cin >> a;

    while(n <= 0){
        cin >> n;
    }

    for(int i = a; i < a+n; i++){
        sum += i;
    }

    cout << sum << "\n";
    return 0;
}