//
// Created by lanys on 2024/4/11.
//
区间求和
#include <iostream>
using namespace std;
int sum(int x, int y) {
int sum = 0;
for (int i = x; i <= y; i++) {
sum += i;
}
return sum;
}
int main() {
int x, y;
cin >> x >> y;
cout << sum(x, y) << endl;
return 0;
}