/* -*- coding: utf-8 -*-
 *
 * 242.cc: No.242 ビンゴゲーム - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int N = 5;
const int NN = N * N;
const int C = 99;

/* typedef */

typedef long double ld;

/* global variables */

ld combs[C + 1][C + 1];

/* subroutines */

/* main */

int main() {
  for (int i = 0; i <= C; i++) {
    combs[i][0] = combs[i][i] = 1.0;
    for (int j = 1; j < i; j++)
      combs[i][j] = combs[i - 1][j - 1] + combs[i - 1][j];
    for (int j = i + 1; j <= N; j++) combs[i][j] = 0.0;
  }

  int n;
  cin >> n;

  ld ans = combs[n][N] / combs[C][N] * (N * 2 + 2);
  printf("%.10Lf\n", ans);
  return 0;
}