#include <bits/stdc++.h>
#define rep(i, n) for(long long i = 0; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
using namespace std;

using lint = long long;
using ld = long double;

int main() {
    lint n, K;
    cin >> n >> K;
    vector<vector<lint>> dp1(n + 1, vector<lint>(70)), dp2(n + 1, vector<lint>(70));
    dp1[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < 70; j++) {
            if (i <= K) {
                for (int k = 4; k <= 6; k++) {
                    if (j - k >= 0) {
                        dp1[i][j] += dp1[i - 1][j - k];
                    }
                }
            } else {
                for (int k = 1; k <= 6; k++) {
                    if (j - k >= 0) {
                        dp1[i][j] += dp1[i - 1][j - k];
                    }
                }
            }
        }
    }
    dp2[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < 70; j++) {
            for (int k = 1; k <= 6; k++) {
                if (j - k >= 0) {
                    dp2[i][j] += dp2[i - 1][j - k];
                }
            }
        }
    }
    lint all = powl(6LL, n) * powl(3LL, K) * powl(6LL, n - K);
    lint cnt = 0;
    for (int taro = 0; taro < 70; taro++) {
        for (int jiro = 0; jiro < taro; jiro++) {
            cnt += dp1[n][taro] * dp2[n][jiro];
        }
    }
    ld ans = (ld)cnt / (ld)all;
    cout << fixed << setprecision(10) << ans << endl;
}