#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
#include<complex>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>
#include<stack>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int K;
    cin >> K;
    vector<double> dp(K+1, 0);
    for (int t = 0; t < 10000; t++) {
        for (int i = 1; i <= K; i++) {
            double tmp = 6;
            for (int j = 1; j <= 6; j++) {
                if (i-j < 0) tmp += dp[K];
                else tmp += dp[i-j];
            }
            dp[i] = tmp/6;
        }
    }
    printf("%.10lf\n", dp[K]);
    return 0;
}