#include <algorithm>
#include <iostream>
using namespace std;
int main(){
	int k;	cin>>k;
	double ans[21];
	ans[0]=1;	ans[1]=1;
	for(int i=0;i<=k;i++){
		ans[i]=0;
		for(int j=1;i-j>0&&j<=6;j++){
			ans[i]+=ans[i-j]/6;
		}
		ans[i]+=1;
	}
	cout<<ans[k]<<endl;
	return 0;
}