#include <stdio.h>
#include <string>
#include <cstring>
#include <stdlib.h>
#include <math.h>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <assert.h>
#pragma warning(disable:4996) 
 
typedef long long ll;
#define MIN(a, b) ((a)>(b)? (b): (a))
#define MAX(a, b) ((a)<(b)? (b): (a))
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define INF 2140000000
//const long long MOD = 1000000007;
const long long MOD = 998244353;

using namespace std;


void solve()
{
    int a, b;
    scanf("%d%d", &a, &b);
    int t = b - a;
    double ans = (double)t*t*t / 6;
    printf("%.10lf\n", ans);    

    return;
}

int main(int argc, char* argv[])
{
#if 1
    solve();
#else
    int T; scanf("%d", &T);
    while(T--) {
        solve();
    }
#endif
    return 0;
}