#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)
#define repl(i,m,n) for(ll i=m; i<n; ++i)

int main(){
    double a, b;
    cin >> a >> b;
    double S = (b - a)*(b - a)*(b - a);
    S = abs(S / 6.0);
    printf("%.7f\n", S);
    return 0;
}