PRADIPSUM.cpp

#include <iostream>
using namespace std;

long long sumAll(long long a, long long b) {
	long long n;

	if (b > a) n = b - a + 1;
	else n = a - b + 1;
	
	return n * (a + b) / 2;
}

int main() {
	ios::sync_with_stdio(false);
	//freopen("input.txt", "r", stdin);

	int a, b;
	while(cin >> a >> b) {
	  cout << sumAll(a, b) << endl;
	}

  return 0;
}