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

#define all(v) v.begin(),v.end()
using ll = long long;
using ull = unsigned long long;
using vll=vector<ll>;
using vvll = vector<vector<ll>>;

int main(){
    ll K;
    cin>>K;
    vector<double> dp(100);
    for(int i=K-1;i>=0;i--){
        for(int j=1;j<=6;j++){
            dp[i]+=dp[i+j]/6;
        }
        dp[i]++;
    }
    cout << dp[0] << endl;
}