#include "bits/stdc++.h"
using namespace std;
#define int long long
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i)
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i)
#define ALL(a) a.begin(), a.end()
#define IN(a, x, b) (a <= x && x < b)
template<class T>inline bool CHMIN(T&a,T b){if(a>b){a = b;return true;}return false;}
template<class T>inline bool CHMAX(T&a,T b){if(a<b){a = b;return true;}return false;}



signed main(){
	int A,B;
	cin >> A >> B;
	printf("%.20lf\n",pow(B - A,3) / 6.0);
}