#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

int N, K;
int cnt[2][61];

void count(int pl, int i, int s) {
	if (i >= N) ++cnt[pl][s];
	else if (pl == 0 && i < K) REP(j, 3) REP(k, 2) count(pl, i + 1, s + j + 4);
	else REP(j, 6) count(pl, i + 1, s + j + 1);
}

int main(int argc, char **argv) {
	cin >> N >> K;
	CLEAR(cnt);
	REP(i, 2) count(i, 0, 0);
	ll c[2] = { 0, 0 };
	REP(i, 61) REP(j, 61) c[i > j ? 0 : 1] += (ll)cnt[0][i] * cnt[1][j];
	cout << fixed << setprecision(5) << ((double)c[0] / (c[0] + c[1])) << endl;
	return 0;
}