#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    int a, b;
    cin >> a >> b;

    int d = b - a;

    printf("%.8f\n", (double)d * d * d / 4 * 2 / 3);

    return 0;
}