#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int k;
    cin >> k;

    double dp[100] = {};

    drep(i,k){
        dp[i] += 1;
        srep(j,1,7){
            if(i - j < 0)break;
            dp[i-j] += dp[i] / 6.0;
        }
    }


    cout << dp[0] << endl;
    return 0;
}