#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <stack>
#include <vector>
#include <set>
#include <utility>
using namespace std;
typedef long long ll;

int main(){
    int a,b;
    cin >> a >> b;
    
    double ans = (b-a)*(b-a)*(b-a)/(double)6;

    printf("%.14lf\n",ans);
}