#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;

int n, k;
int c1[61], c2[61];

void dfs1(int m=0, int acc=0) {
    if (m == n) {
        c1[acc] += 1;
        return;
    }
    for(int i = 1; i <= 6; i++) dfs1(m+1, acc+i);
}

void dfs2(int m=0, int acc=0) {
    if (m == n) {
        c2[acc] += 1;
        return;
    }
    if (m < k) for(int i: {4,4,5,5,6,6}) dfs2(m+1, acc+i);
    else for(int i = 1; i <= 6; i++) dfs2(m+1, acc+i);
}

int main() {
    cin >> n >> k;
    dfs1();
    dfs2();
    for(int i = 59; i >= 0; i--) c2[i] += c2[i+1];
    ll wincnt = 0;
    rep(i, 60) wincnt += ll(c1[i]) * c2[i+1];
    ll totcnt = 1;
    rep(_, 2*n) totcnt *= 6;
    printf("%.8f\n", double(wincnt) / totcnt);
}