#include <bits/stdc++.h>

#define show(x) cout << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;


int main()
{
    int N, K;
    cin >> N >> K;
    mt19937 mt(random_device{}());
    uniform_int_distribution<int> d1{1, 6};
    uniform_int_distribution<int> d2{4, 6};
    constexpr int t = 3000000;
    int cnt = 0;
    for (int i = 0; i < t; i++) {
        int sum1 = 0;
        int sum2 = 0;
        for (int k = 0; k < N; k++) {
            sum2 += d1(mt);
        }
        for (int k = 0; k < K; k++) {
            sum1 += d2(mt);
        }
        for (int k = 0; k < N - K; k++) {
            sum1 += d1(mt);
        }
        if (sum1 > sum2) {
            cnt++;
        }
    }
    cout << fixed << setprecision(10) << (long double)(cnt) / t << endl;

    return 0;
}