#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; double w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int foo(int N, int K) {
	int res = 0;
	for (int i = 0; i < K; i++)
		res += 4 + rand() % 3;
	for (int i = 0; i < N - K; i++)
		res += 1 + rand() % 6;
	return res;
}

int main() {
	int N, K; cin >> N >> K;
	int cnt = 0;
	for (int i = 0; i < 10000000; i++)
		if (foo(N, K) > foo(N, 0)) cnt++;
	cout << (double)cnt / 10000000 << endl;
}