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

#define all(c) ((c).begin()), ((c).end())
#define dump(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define REP(i, a, b) for (int i = a; i < (int)(b); i++)
#define rep(i, n) REP(i, 0, n)
#define mp make_pair
#define fst first
#define snd second
#define pb push_back
#define debug( fmt, ... ) \
        fprintf( stderr, \
                  fmt "\n", \
                  ##__VA_ARGS__ \
        )

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int INF = 1 << 29;
const double EPS = 1e-10;

double zero(double d) {
    return d < EPS ? 0.0 : d;
}
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );

template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
    return os << '(' << p.first << ',' << p.second << ')';
}

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &a) {
    os << '[';
    rep(i, a.size()) os << (i ? " " : "") << a[i];
    return os << ']';
}

string toString(int i) {
    stringstream ss;
    ss << i;
    return ss.str();
}

const int MOD = 1000000007;
// a^k
ll fpow(ll a, ll k, int M) {
    ll res = 1ll;
    ll x = a;
    while (k != 0) {
        if ((k & 1) == 1)
            res = (res * x) % M;
        x = (x * x) % M;
        k >>= 1;
    }
    return res;
}

struct prepare {
	prepare() {
	    cout.setf(ios::fixed, ios::floatfield);
	    cout.precision(8);
	    ios_base::sync_with_stdio(false);
	}
} _prepare;

int main() {
    int N, K;
    cin >> N >> K;

    const int MAX_SUM = 60 + 10;

    vvi dp_a(N+1, vi(MAX_SUM, 0));
    vll acc_a(MAX_SUM, 0);
    {
        dp_a[0][0] = 1;
        rep(i, N) {
            rep(j, MAX_SUM) {
                if (dp_a[i][j] == 0)
                    continue;

                REP(k, 1, 6 + 1)
                    dp_a[i + 1][j + k] += dp_a[i][j];
            }
        }
        REP(i, 1, MAX_SUM)
            acc_a[i] = acc_a[i-1] + dp_a[N][i];
    }
    vvi dp_b(N+1, vi(MAX_SUM, 0));
    vll acc_b(MAX_SUM, 0);
    {
        dp_b[0][0] = 1;
        rep(i, K) {
            rep(j, MAX_SUM) {
                if(dp_b[i][j] == 0)
                    continue;

                REP(k, 4, 6 + 1)
                    dp_b[i+1][j+k] += dp_b[i][j];
                REP(k, 4, 6 + 1)
                    dp_b[i+1][j+k] += dp_b[i][j];
            }
        }
        REP(i, K, N) {
            rep(j, MAX_SUM) {
                if (dp_b[i][j] == 0)
                    continue;

                REP(k, 1, 6 + 1)
                    dp_b[i + 1][j + k] += dp_b[i][j];
            }
        }
        REP(i, 1, MAX_SUM)
            acc_b[i] = acc_b[i-1] + dp_b[N][i];
    }

    double win = 0;
    REP(i, 1, MAX_SUM){
        win += acc_a[i-1] * dp_b[N][i];
    }
    rep(i, N)
        win /= 36.0;

    cout << win << endl;
    
    return 0;
}