#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++)
#define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++)
#define all(n) (n).begin(),(n).end()
typedef long long ll;
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef pair<long long,long long> Pii;
typedef vector<Pii> VPii;


double dp[114][114][114];
bool ok[114][114][114];

int N,K;
double dfs(int x,int a,int b){
	if( x == 0 ) return a < b;
	if( ok[x][a][b] ) return dp[x][a][b];
	
	double ans = 0;
	int c = 0;
	for(int i = 1 ; i <= 6 ; i++){
		for(int j = (x<=K?4:1) ; j <= 6 ; j++){
			ans += dfs(x-1,a+i,b+j);
			c++;
		}
	}
	ok[x][a][b] = true;
	return dp[x][a][b] = ans / c;
}

int main(){
	
	cin >> N >> K;
	printf("%.10lf\n",dfs(N,0,0));
	
}