#include <bits/stdc++.h>
using namespace std;
using lint     = long long;
const lint inf = 1LL << 60;
const lint mod = 1000000007;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    double a, b;
    cin >> a >> b;
    double ret = 0;
    ret += (b * b * b - a * a * a) / 3.0;
    ret -= (b * b - a * a) * (a + b) / 2.0;
    ret += (b - a) * a * b;
    cout << fixed << setprecision(10) << -ret << "\n";
    return 0;
}