#include <iostream>
#include <cmath>
#include <vector>
#include <string>
#include <map>
#include <queue>
#include <algorithm>
#include <numeric>
#include <fstream>
#include <iomanip>

typedef long double ld;
typedef long long ll;
const ll INF = (ll)1e18 + 1;
const ll MOD = 998244353;


namespace util {

// 文字列のSplit
std::vector< std::string > split(std::string s, char delimiter)
{
  std::vector< std::string > vs;
  std::string sub;
  for (auto c : s) {
    if (c == delimiter) vs.push_back(sub), sub.clear();
    else sub += c;
  }
  vs.push_back(sub);
  return vs;
}

// 文字列の置換
void replaceString(std::string& str, std::string& from, std::string& to, std::string& replaced)
{
  ll from_length = (ll)from.length();

  for (auto it = str.begin(); it != str.end(); it++) {
    std::string sub = str.substr(std::distance(str.begin(), it), from_length);
    if (sub == from) {
      replaced += to;
      it += from_length - 1;
    } else {
      replaced += *it;
    }
  }
}

// 累乗
template < class S, class T >
S pow(S x, T n)
{
  ll ret = 1LL;
  while (n > 0) ret *= x, n--;
  return ret;
}

// 桁和
ll digitSum(ll x)
{
  std::string s = std::to_string(x); ll ret = 0LL;
  for (auto c : s) {ret += c - '0';}
  return ret;
}

} // namespace util

// Minimum, Maximum
template<class T> T minimum(T head, T tail) { return std::min(head, tail); }
template<class H, class... T> H minimum(H head, T... tail) { return std::min(head, minimum(tail...)); }
template<class T> T maximum(T head, T tail) { return std::max(head, tail); }
template<class H, class... T> H maximum(H head, T... tail) { return std::max(head, maximum(tail...)); }

// Output
template<class T, class S> std::ostream& operator <<(std::ostream& os, std::pair<T, S> p)
{
  return os << "(" << p.first << " " << p.second << ")";
}

template<class T> std::ostream& operator <<(std::ostream& os, std::vector< T > v)
{
  for (ll i = 0; i < (ll)v.size(); i++){ os << " [" << i << "]" << v[i]; if (i % 10 == 9) os << std::endl; }
  //os << v[0]; for (ll i = 1; i < (ll)v.size(); i++){ os << " " << v[i]; }
  return os;
}

template<class T, class S> std::ostream& operator <<(std::ostream& os, std::map< T, S > m)
{
  ll i = 0; for (auto p : m){ os << " [" << i << "]" << p.first << "->" << p.second; i++;}
  return os;
}

template<class T> std::ostream& operator <<(std::ostream& os, std::vector< std::vector<T> > vv)
{
  for (auto& vec : vv){ os << vec << std::endl; }
  os << "--------" << std::endl;
  return os;
}

void print(){ std::cout << std::endl; }
template<typename H> void print(H&& head){ std::cout << head << std::endl; }
template<typename H, typename... T> void print(H&& head, T&&... tail){
  std::cout << head << " ", print(std::forward<T>(tail)...);
}

// GCD, LCM
ll gcd(ll a, ll b) {
  while (b != 0) { a %= b; std::swap(a, b); }
  return a;
}
ll lcm(ll a, ll b) { return (a / gcd(a, b)) * b; }

// DIGNUM
std::vector<ll> dignum(ll x) {
  if (x == 0) return {0};
  std::vector<ll> res;
  while (x) {
    res.push_back(x % 10);
    x /= 10;
  }
  std::reverse(res.begin(), res.end());
  return res;
}

// FAIL
void fail(){ print(0); std::exit(0); }

void solve()
{
  ll N;
  std::cin >> N;
  ll d;

  std::vector< ll > vcnt(N-1, 0LL);

  std::cin >> d;
  if (d != 0) fail();
  vcnt[0] = 1LL;

  ll dmax = 0;
  for (ll i = 1; i < N; i++) {
    std::cin >> d;
    if (d == 0LL) fail();
    vcnt[d]++;
    dmax = std::max(dmax, d);
  }

  ll ans = 1LL;
  for (ll d = 1; d <= dmax; d++) {
    for (ll i = 0; i < vcnt[d]; i++) {
      ans = (ans * vcnt[d-1]) % MOD;
    }
  }

  print(ans);
  return;
}

int main()
{
  std::cin.tie(nullptr);
  std::cout.tie(nullptr);
  std::ios::sync_with_stdio(false);

  solve();
  return 0;
}



Measured memory_bytes: 1024