#include<iostream>
#include<cstdlib>
#include<ctime>

using namespace std;

#define NUM 1000000

int main(){

	int K;
	int c=NUM;
	long long sum=0;
	
	cin>>K;

	while(c--){
		int xi=0;
		while(xi<K){
			sum+=1;
			xi+=rand()%6+1;
		}
	}

	cout<<(double)sum/NUM<<endl;
}