#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
#include <stack>
#include <queue>
#include <set>
using namespace std;

//#define __int64 long long
#define long __int64
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vec = 4;
const int Vecy[Vec] = {0,-1,0,1};
const int Vecx[Vec] = {1,0,-1,0};
const int Modd = 1000000007;

double dp[30] = {0};
int main(){
	int k;
	cin >> k;
	
	for(int i=k-1; i>=0; i--){
		for(int j=1; j<=6; j++){
			dp[i] += dp[i + j];
		}
		dp[i] = dp[i] / 6 + 1;
	}
	
	cout << dp[0] << endl;
    
    return 0;
}