#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++)
#define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++)
#define all(n) (n).begin(),(n).end()
typedef long long ll;
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef pair<long long,long long> Pii;
typedef vector<Pii> VPii;
typedef complex<double> P;

double dp[21];
double f(long long x){
	if( x <= 0 ) return 0;
	if( dp[x] ) return dp[x];
	return dp[x] = (f(x-1) + f(x-2) + f(x-3) + f(x-4) + f(x-5) + f(x-6)) / 6. + 1;
}

int main(){
	int K;
	cin >> K;
	printf("%.10lf\n",f(K));
}