// vvvvvvvvvvvv TEMPLATE vvvvvvvvvvvv
#include <bits/stdc++.h>
using namespace std; using ll = long long; using P = pair<ll, ll>;
const ll linf = 1e18; const double eps = 1e-12, pi = acos(-1);
#define FOR(i,a,b) for (ll i=(a),__last_##i=(b);i<__last_##i;i++)
#define RFOR(i,a,b) for (ll i=(b)-1,__last_##i=(a);i>=__last_##i;i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define each(i,a) for (auto&& i : a)
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)
#define pb push_back
#define eb emplace_back
#define all(a) begin(a),end(a)
#define chmin(x,v) x = min(x, v)
#define chmax(x,v) x = max(x, v)
template<typename Head> void out(Head h) { cout << h << endl; } template<typename Head, typename... Tail>void out(Head h, Tail... t) { cout << h << " "; out(t...); }
template<typename T> istream& operator>>(istream& is, vector<T>& v) { each(x,v) is >> x; return is; }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) { rep(i,v.size()) { if (i) os << " "; os << v[i]; } return os; }
ostream& operator<<(ostream& os, const vector<string>& v) { rep(i,v.size()) { if (i) os << endl; os << v[i]; } return os; }
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v) { rep(i,v.size()) { if (i) os << endl; os << v[i]; } return os; }
template<typename T1, typename T2> ostream& operator<<(ostream& os, const pair<T1, T2>& p) { return os << "(" << p.first << ", " << p.second << ")"; }
struct yes_no : std::numpunct<char> { string_type do_truename() const { return "Yes"; } string_type do_falsename() const { return "No"; } };
void solve(); int main() {
  ios::sync_with_stdio(false); cin.tie(0); locale loc(locale(), new yes_no); cout.imbue(loc); cout << fixed << setprecision(10) << boolalpha;
  solve();
}
// ^^^^^^^^^^^^ TEMPLATE ^^^^^^^^^^^^

constexpr ll mod = 998244353;
constexpr ll mul(ll a, ll b) { return a * b % mod; }
ll mul(initializer_list<ll> t) { ll res = 1; each(v, t) res = mul(res, v); return res; }
ll add(ll a, ll b) { return (a + b) % mod; }
ll add(initializer_list<ll> t) { ll res = 0; each(v, t) res = add(res, v); return res; }
ll sub(ll a, ll b) { return (a - b + mod) % mod; }
ll sub(initializer_list<ll> t) { auto it = t.begin(); ll res = *(it++); while (it != t.end()) res = sub(res, *(it++)); return res; }
ll inv(ll n); ll power(ll x, ll n) { if (n < 0) return inv(power(x, -n)); ll res = 1; for (ll i = 1; i <= n; i <<= 1) { if (i & n) res = mul(res, x); x = mul(x, x); } return res; }
ll inv(ll n) { return power(n, mod-2); }
ll divi(ll a, ll b) { return mul(a, inv(b)); }
ll divi(initializer_list<ll> t) { auto it = t.begin(); ll res = *(it++); while (it != t.end()) res = divi(res, *(it++)); return res; }
vector<ll> fact, rfact;
void init_fact(ll n) { fact.resize(n+1); fact[0] = 1; rep(i, n) fact[i+1] = mul(fact[i], i+1); rfact.resize(n+1); rfact[n] = inv(fact[n]); rrep(i, n) rfact[i] = mul(rfact[i], i+1); }
ll comb(ll n, ll r) { if (r < 0) return 0; if (r > n) return 0; return divi(fact[n], mul(fact[r], fact[n-r])); }
ll perm(ll n, ll r) { if (r < 0) return 0; if (r > n) return 0; return divi(fact[n], fact[n-r]); }

using Row = vector<ll>;
using Matrix = vector<Row>;
Matrix E(ll n) { Matrix res(n, Row(n, 0)); rep(i, n) res[i][i] = 1; return res; }
Matrix mul(const Matrix& A, const Matrix& B) { const ll n = A.size(), m = A[0].size(), l = B[0].size(); assert(m == B.size()); Matrix res(n, Row(l, 0)); rep(i, n) rep(j, m) rep(k, l) res[i][k] = add(res[i][k], mul(A[i][j], B[j][k])); return res; }
Row mul(const Matrix& A, const Row& x) { Matrix tx(x.size()); rep(i, x.size()) tx[i] = Row(1, x[i]); tx = mul(A, tx); Row res(x.size()); rep(i, x.size()) res[i] = tx[i][0]; return res; }
Matrix power(Matrix A, ll n) { assert(A.size() == A[0].size()); Matrix res = E(A.size()); for (ll i = 1; i <= n; i <<= 1) { if (i & n) res = mul(res, A); A = mul(A, A); } return res; }

ll solve(const vector<ll>& d) {
  const ll n = d.size();
  if (d[0] != 0) return 0;
  vector<ll> cnt(n, 0);
  rep(i, n) ++cnt[d[i]];
  if (cnt[0] > 1) return 0;
  ll res = 1;
  rep(i, 1, n) {
    res = mul(res, power(cnt[i-1], cnt[i]));
  }
  return res;
}

void solve() {
  ll n; cin >> n;
  vector<ll> d(n); cin >> d;
  cout << solve(d) << endl;
}


Measured memory_bytes: 1792