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

int main() {
    int k;
    cin>>k;
    double dp[k+6] {};
    for (int i=k-1;i>=0;i--) {
        dp[i] = 1;
        for (int j=1;j<=6;j++) dp[i] += dp[i+j]/6;
    }
    cout << dp[0] << endl;
    return 0;
}