#include <iostream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <cassert>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <string>
#include <algorithm>
#define llint long long
#define inf 1e18
#define rep(x, s, t) for(llint (x) = (s); (x) < (t); (x)++)
#define Rep(x, s, t) for(llint (x) = (s); (x) <= (t); (x)++)

using namespace std;

double a, b;

int main(void)
{
	//ios::sync_with_stdio(0);
	//cin.tie(0);
	
	cin >> a >> b;
	double ans = a-b;
	ans = ans*ans*ans;
	
	printf("%.11f\n", fabs(ans/6));
	
	return 0;
}