#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;


int main(){
    int k;
    double anst = 0;
    cin >> k;
    vector<double> dice(k+1);
    dice[1] = 1.0;
    for (int i = 2; i <= k; i++){
        for (int l = 1; l <= 6; l++){
            if (i - l >= 0) dice[i] += dice[i-l]/6;
        }
        dice[i]++;
    }
    cout << dice[k] << endl;
}