#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <map>
#include <numeric>
using namespace std;
typedef long long LL;

vector<double> memo(21, -1.0);

double solve(int K){
    if(K <= 0) return 0.0;
    if(memo[K] >= 0.0) return memo[K];
    double exp = 0.0;
    for(int i = 1; i <= 6; i++){
        exp += 1.0/6.0 * (solve(K-i) + 1.0);
    }
    memo[K] = exp;
    return exp;
}

int main(){
    LL K;
    cin >> K;
    cout << setprecision(13) << solve(K) << endl;
    return 0;
}