#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, srt, end) for (long long i = (srt); i < (long long)(end); i++)

int main(){
    double a, b;
    cin >> a >> b;
    double ans = (pow(b,3)-pow(a,3))/3 - (a+b)*(b*b-a*a)/2 + a*b*(b-a);
    cout << abs(ans) << endl;
    return 0;
}