#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;


int K;
double memo[20];

double dfs( int x ) {
    
    if ( x >= K ) { return 0; }
    
    if ( memo[x] != -1 ) { return memo[x]; }
    
    memo[x] = dfs( x+1 ) / 6 + dfs( x+2 ) / 6 + dfs( x+3 ) / 6 
        + dfs( x+4 ) / 6 + dfs( x+5 ) / 6 + dfs( x+6 ) / 6 + 1;
    
    return memo[x];
}


int main() {
    
    cin >> K;
    fill( memo, memo+20, -1 );
    
    dfs(0);
    
    cout << memo[0] << endl;
    
    return 0;
}