#include <bits/stdc++.h>

typedef long long ll;
 
using namespace std;
 
//const int MAX=INT_MAX;
 
//const ll MAX=100000000000;
const ll MAX=90000000000000;
const int mod = 1000000007;
//const int mod = 998244353;
 
//const ll A=100000000000;

vector<double >dp;

int main(){
    
    int K;
    
    cin>>K;
    
    dp.assign(K+7, 0);
    
    for(int i=K-1;i>=0;i--){
        for(int x=1;x<=6;x++){
            dp[i]+=(dp[i+x]+1)/6.0;
        }
    }
    
    printf("%.7lf\n",dp[0]);
    
}