#include <iostream>
#include <vector>
using namespace std;

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

    // 太郎
    vector<vector<double>> dp1(N + 1, vector<double>(6 * N + 1, 0)); 
    // 二郎
    vector<vector<double>> dp2(N + 1, vector<double>(6 * N + 1, 0));
    dp1[0][0] = 1;
    dp2[0][0] = 1;
    for (int i = 1; i <= N; ++i) {
        for (int j = 1; j <= 6 * i; ++j) {
            if (i <= K) {
                for (int k = 4; k <= 6; ++k) {
                    if (j - k >= 0) {
                        dp1[i][j] += dp1[i - 1][j - k] / 3.0;
                    }
                }
            } else {
                for (int k = 1; k <= 6; ++k) {
                    if (j - k >= 0) {
                        dp1[i][j] += dp1[i - 1][j - k] / 6.0;
                    }
                }
            }
        }
    }


    for (int i = 1; i <= N; ++i) {
        for (int j = 1; j <= 6 * i; ++j) {
            for (int k = 1; k <= 6; ++k) {
                if (j - k >= 0) {
                    dp2[i][j] += dp2[i - 1][j - k] / 6.0;
                }
            }
        }
    }

    double res = 0;
    for (int i = 1; i <= 6 * N; ++i) {
        for (int j = 1; j < i; ++j) {
            res += dp1[N][i] * dp2[N][j];
        }
    }

    cout << res << endl;
}