#include <algorithm>
#include <cmath>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;
using ll = long long;

int N, K;

bool trial(mt19937 &mt) {
    int taro = 0;
    int jiro = 0;

    for (int i = 0; i < K; i++) {
        taro += mt() % 3 + 4;
        jiro += mt() % 6 + 1;
    }

    for (int i = 0; i < N - K; i++) {
        taro += mt() % 6 + 1;
        jiro += mt() % 6 + 1;
    }

    return taro > jiro;
}

double monte(mt19937 &mt) {
    int win = 0;
    int lose = 0;
    for (int i = 0; i < 1000000; i++) {
        if (trial(mt)) {
            win++;
        } else {
            lose++;
        }
    }

    return (win * 1.0 / (win + lose));
}

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

    random_device rnd;
    mt19937 mt(rnd());

    cin >> N >> K;

    cout << monte(mt) << endl;

    return 0;
}