/* -*- coding: utf-8 -*-
 *
 * 1904.cc:  No.1904 Never giving up! - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 20;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];
ll fs[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i);
  sort(as, as + n);

  fs[0] = 1;
  for (int i = 1; i <= n; i++) fs[i] = fs[i - 1] * i;

  ll p = 1;
  for (int i = 0; i < n;) {
    int j = i;
    while (i < n && as[j] == as[i]) i++;
    p *= fs[i - j];
  }

  printf("%lld\n", fs[n] / p);

  return 0;
}