#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using vd  = vector<double>;
using vvd = vector<vd>;

#define REP(i,n) for(ll i=0; i<(n); ++i)
#define FOR(i,b,n) for(ll i=(b); i<(n); ++i)

int main() {
	cout << fixed << setprecision(30);
	ll n, k; cin >> n >> k;
	vvd dp1(11, vd(61, 0));
	vvd dp2(11, vd(61, 0));
	dp1[0][0] = dp2[0][0] = 1;
	REP(i, n) REP(j,61){
		FOR(l, 1, 7) if(j + l < 61) dp1[i + 1][j + l] += dp1[i][j] / 6;
		if (k > i) {
			FOR(l, 4, 7) if (j + l < 61)  dp2[i + 1][j + l] += dp2[i][j] / 3;
		} else {
			FOR(l, 1, 7) if (j + l < 61)  dp2[i + 1][j + l] += dp2[i][j] / 6;
		}
	}
	
	double ans = 0;
	FOR(i, 1, 61) for (ll j = i-1; j >= 0; --j) ans += dp2[n][i] * dp1[n][j];
	cout << ans << endl;
	return 0;
}