#include<iostream>
using namespace std;
#define MAX 61
#define REP(i,n) for(int i=0;i<n;i++)
#define rep(i,s,n) for(int i=s;i<n;i++)
double dp1[MAX];
double dp2[MAX];
int main(){
	int n, k; cin >> n >> k;
	dp1[0] = dp2[0] = 1;
	REP(i,n){
		for (int j = MAX - 10; j >= 0; j--){
			for (int k = 1; k <= 6; k++){
				dp1[j + k] += dp1[j] / 6;
			}
			dp1[j] = 0;
		}
	}
	REP(i,k){
		for (int j = MAX - 10; j >= 0; j--){
			for (int k = 4; k <= 6; k++){
				dp2[j + k] += dp2[j] / 3;
			}
			dp2[j] = 0;
		}
	}
	rep(i,k,n){
		for (int j = MAX - 10; j >= 0; j--){
			for (int k = 1; k <= 6; k++){
				dp2[j + k] += dp2[j] / 6;
			}
			dp2[j] = 0;
		}
	}
	double ans = 0;
	REP(i,MAX) rep(j, i + 1, MAX){
		ans += dp1[i] * dp2[j];
	}
	printf("%.13f\n", ans);
	return 0;
}