#include <stdio.h>
#include <math.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <numeric>
#include <string>
#include <map>
#include <stack>
using namespace std;
typedef long long int lli;
#define urept(soeji, start, n) for (int soeji = start; soeji < n; soeji++)
#define drept(soeji, start, n) for (int soeji = start; soeji > n; soeji--)
int main(void)
{
    int a, b;
    cin >> a >> b;
    double ans = (b - a) * (b - a) * (b - a);
    ans = ans / 6;
    printf("%.7f", ans);
    return 0;
}