#include "bits/stdc++.h"
 
using namespace std;
typedef long long int ll;
typedef pair<ll, ll > pi;  
typedef pair<pair<ll, ll >, ll > pii;  
vector<ll > vec;
vector<vector<ll > > vec2;
ll MOD = 1000000007;
ll INF = 1145141919454519;

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

    cout << fixed << std::setprecision(15) << abs(-((b-a)*(b-a)*(b-a))/6) << endl;

    
}