#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

vd Gauss(vvd A,vd b){
	int n=A.size();
	vvd B=A;
	for(int i=0;i<n;i++) B[i].push_back(b[i]);
	for(int i=0;i<n;i++){
		int I=i;
		for(int j=i;j<n;j++){
			if(fabs(B[j][i])>fabs(B[I][i])) I=j;
		}
		swap(B[i],B[I]);
		if(abs(B[i][i])<eps) return vd();
		for(int j=i+1;j<=n;j++) B[i][j]/=B[i][i];
		for(int j=0;j<n;j++) if(i!=j){
			for(int k=i+1;k<=n;k++) B[j][k]-=B[j][i]*B[i][k];
		}
	}
	vd x(n);
	for(int i=0;i<n;i++) x[i]=B[i][n];
	return x;
}

int n;

int main(){
	cin>>n;
	vvd A(n,vd(n));
	for(int i=0;i<n;i++){
		A[i][i]=1;
		for(int j=1;j<7;j++) if(i+j!=n){
			int I=(i+j>n?0:i+j);
			A[i][I]-=1.0/6;
		}
	}
	cout<<syosu(9)<<Gauss(A,vd(n,1))[0]<<endl;
}