#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
    int k; cin>>k;
    double p[210], e[210];
    e[0]=0, p[0]=1;
    for(int i=1; i<=k; i++){
        p[i]=0, e[i]=1;
        for(int j=0; j<6; j++){
            if(i-1-j>=0){
                p[i]+=p[i-1-j]/6.0;
                e[i]+=e[i-1-j]/6.0;
            }
        }
    }
    printf("%.6lf\n", e[k]/p[k]);
    return 0;
}