#include <iostream>
#include <iomanip>
#include <vector>

using ldouble = long double;

std::vector<ldouble> calc(int n, int k) {
    int m = n * 6;

    std::vector<ldouble> dp(m + 1, 0);
    auto ndp = dp;

    dp[0] = 1;

    for (int i = 0; i < n; ++i) {
        std::fill(ndp.begin(), ndp.end(), 0);

        for (int d = 0; d <= m; ++d) {
            if (i < k) {
                for (int f = 4; f <= 6; ++f) {
                    if (d + f > m) continue;
                    ndp[d + f] += dp[d] / 3;
                }
            } else {
                for (int f = 1; f <= 6; ++f) {
                    if (d + f > m) continue;
                    ndp[d + f] += dp[d] / 6;
                }
            }
        }

        std::swap(dp, ndp);
    }

    return dp;
}

void solve() {
    int n, k;
    std::cin >> n >> k;

    int m = n * 6;
    auto adp = calc(n, 0),
         bdp = calc(n, k);

    ldouble ans = 0;
    for (int b = 0; b <= m; ++b) {
        for (int a = 0; a < b; ++a) {
            ans += adp[a] * bdp[b];
        }
    }

    std::cout << std::fixed << std::setprecision(10)
              << ans << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}