/* -*- coding: utf-8 -*-
 *
 * 1009.cc:  No.1009 面積の求め方 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

// f(x) = (x-a)(x-b) = x^2-(a+b)x+ab
// F(x) = x^3/3-(a+b)x^2/2+abx

double F(double x, int a, int b) {
  return x * x * x / 3 - (a + b) * x * x / 2 + a * b * x;
}

/* main */

int main() {
  int a, b;
  scanf("%d%d", &a, &b);

  printf("%.7lf\n", -(F(b, a, b) - F(a, a, b)));
  return 0;
}