#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std; // NOLINT

int main() {
    int32_t k;
    cin >> k;
    vector<double> dp(k + 6);
    for (auto i = k - 1; i >= 0; --i) {
        double s = 1;
        for (auto j = 1; j <= 6; ++j) {
            s += dp[i + j] / 6;
        }
        dp[i] = s;
    }
    printf("%.9f\n", dp[0]);
    return 0;
}