#include <bits/stdc++.h>

using namespace std;

double dp1[61], dp2[61], tmp[61];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, K;
    cin >> N >> K;
    dp1[0] = 1.0;
    dp2[0] = 1.0;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j <= 60; j++) tmp[j] = 0;
        for (int j = 0; j <= 60; j++) {
            for (int k = 1; k <= 6; k++) {
                if (j + k > 60) continue;
                tmp[j + k] += dp1[j] / 6;
            }
        }
        for (int j = 0; j <= 60; j++) dp1[j] = tmp[j];
    }
    for (int i = 0; i < N - K; i++) {
        for (int j = 0; j <= 60; j++) tmp[j] = 0;
        for (int j = 0; j <= 60; j++) {
            for (int k = 1; k <= 6; k++) {
                if (j + k > 60) continue;
                tmp[j + k] += dp2[j] / 6;
            }
        }
        for (int j = 0; j <= 60; j++) dp2[j] = tmp[j];
    }
    for (int i = 0; i < K; i++) {
        for (int j = 0; j <= 60; j++) tmp[j] = 0;
        for (int j = 0; j <= 60; j++) {
            for (int k = 4; k <= 6; k++) {
                if (j + k > 60) continue;
                tmp[j + k] += dp2[j] / 3;
            }
        }
        for (int j = 0; j <= 60; j++) dp2[j] = tmp[j];
    }
    double ans = 0.0;
    for (int i = 0; i <= 60; i++) {
        double p = 0.0;
        for (int j = i + 1; j <= 60; j++) {
            p += dp2[j];
        }
        ans += p * dp1[i];
    }
    cout << ans << endl;
    return 0;
}