#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <climits>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <stack>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <sstream>
#include <functional>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n)  FOR(i,0,n)
#define CLEAR(d) memset((d), 0, (sizeof((d))))
#define ALL(c) (c).begin(), (c).end()
#define SORT(x) sort((x).begin(), (x).end())
#define RSORT(x) sort((x).begin(), (x).end(), greater<int>() )
#define SIZE(a) ((int)((a).size()))
#define MAX3(a, b, c) (max(max((a), (b)), (c)))
#define MIN3(a, b, c) (min(min((a), (b)), (c)))
#define MOD 1000000007
#define EPS 1e-5
#define PI  (acos(-1))
#define INF 10000000
struct edge{ int to, cost; };
//===================================================

int xor128()
{
    static int x = 123456789;
    static int y = 362436069;
    static int z = 521288629;
    static int w = 88675123;
    int t = x ^ (x << 11);
    x = y; y = z; z = w;
    return w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
}



int main()
{
    int n, k, win = 0, play = 0;
    cin >> n >> k;
    for (play = 0; play < 1000000; play++) {
        int sum1 = 0, sum2 = 0;
        for (int i = 0; i < n; i++) {
            sum1 += xor128() % 6 + 1;
            if (i < n - k) {
                sum2 += xor128() % 6 + 1;
            }
            else {
                sum2 += xor128() % 3 + 4;
            }
        }
        if (sum2 > sum1) win++;
    }
    printf("%f\n", (double)win / play);

    return 0;
}