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

#define int long long

#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define pb push_back
#define all(v) (v).begin(),(v).end()
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;

double dp[100];

signed main(){
    int K;cin>>K;
    for(int i=K-1;i>=0;i--){
        double a=0;
        for(int j=1;j<=6;j++)a+=dp[i+j]/6;
        dp[i]=a+1;
    }
    printf("%.20lf\n",dp[0]);
    return 0;
}