#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  vector<ull> fact(n + 1, 1);
  for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
  vector<int> cnt(n + 1, 0);
  rep(i, n) cnt[a[i]]++;
  ull ans = fact[n];
  rep(i, n + 1) if (cnt[i] > 1) ans /= fact[cnt[i]];
  cout << ans << '\n';
  return 0;
}