#include<iostream>
#include<algorithm>
#include<string>
#include<math.h>
#include<bitset>
#include <vector>
#include<bitset>
#include <iomanip>
#include <map>
#include <set>
#include <stack>
#include <deque>
#include <climits>
#include <queue>
using namespace std;


int main() {
	
	
	double A, B;
	cin >> A >> B;
	double D = (B - A) * (B - A) * (B - A) / 6;
	printf("%.10f\n", D);


	
}