#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <ctime>
#include <cstdlib>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<29;
const ld eps=1e-6;
const LL mod=1e+6 + 3;

int main() {
	int N, K;
	cin >> N >> K;
	int l = 10000000 / N;
	int t = 0, j = 0;
	srand(time(NULL));
	while(l--){
		int taro = 0, jiro = 0;
		REP(i,K)
			taro += rand() % 3 + 4;
		FOR(i,K,N)
			taro += rand() % 6 + 1;
		REP(i,N)
			jiro += rand() % 6 + 1;
		if(taro > jiro)
			t++;
		else if(taro < jiro)
			j++;
	}
	l = 10000000 / N;
	cout << fixed << (double)t/(double)l << endl;
 	return 0;
}