#include <bits/stdc++.h>
#define int long long 
using namespace std;
using Graph = vector<vector<int>>;

signed main(){
  cout << fixed << setprecision(10);
  double A, B;
  cin >> A >> B;
  double ans = (A-B)*(A-B)*(A-B)/6.00000000000;
  cout << abs(ans) << endl;
    
}