#include <bits/stdc++.h>
using namespace std;

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

    mt19937 mt;

    int cnt = 0, MAX = 1000000;
    for (int times = 0; times < MAX; times++) {
        int tarou = 0, jirou = 0;
        for (int i = 0; i < N; i++) {
            jirou += mt() % 6 + 1;
            tarou += (i < K ? mt() % 3 + 4 : mt() % 6 + 1);
        }
        if (tarou > jirou)
            cnt++;
    }

    cout << (double)cnt / MAX << endl;
}