#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
//#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
template<int MOD> struct ModInt {
	static const int Mod = MOD; unsigned x; ModInt() : x(0) { }
	ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
	ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
	int get() const { return (int)x; }
	ModInt& operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
	ModInt& operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
	ModInt& operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
	ModInt& operator/=(ModInt that) { return *this *= that.inverse(); }
	ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
	ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
	ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
	ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
	ModInt inverse() const {
		long long a = x, b = MOD, u = 1, v = 0;
		while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); }
		return ModInt(u);
	}
	bool operator==(ModInt that) const { return x == that.x; }
	bool operator!=(ModInt that) const { return x != that.x; }
	ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }
};
template<int MOD> ostream& operator<<(ostream& st, const ModInt<MOD> a) { st << a.get(); return st; };
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
	ModInt<MOD> r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r;
}
template<typename T, int FAC_MAX> struct Comb {
	vector<T> fac, ifac;
	Comb() {
		fac.resize(FAC_MAX, 1); ifac.resize(FAC_MAX, 1); rep(i, 1, FAC_MAX)fac[i] = fac[i - 1] * i;
		ifac[FAC_MAX - 1] = T(1) / fac[FAC_MAX - 1]; rrep(i, FAC_MAX - 2, 1)ifac[i] = ifac[i + 1] * T(i + 1);
	}
	T aPb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b]; }
	T aCb(int a, int b) { if (b < 0 || a < b) return T(0); return fac[a] * ifac[a - b] * ifac[b]; }
	T nHk(int n, int k) {
		if (n == 0 && k == 0) return T(1); if (n <= 0 || k < 0) return 0;
		return aCb(n + k - 1, k);
	} // nHk = (n+k-1)Ck : n is separator
	T pairCombination(int n) { if (n % 2 == 1)return T(0); return fac[n] * ifac[n / 2] / (T(2) ^ (n / 2)); }
	// combination of paris for n
};
typedef ModInt<998244353> mint;
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     @hamayanhamayan
　　　　／　　　＼　 　  |　|
　　　 /　　 /￣￣￣￣/　　|
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿
　 　　　＼/＿＿＿＿/　（u　⊃
---------------------------------------------------------------------------------------------------*/













int N, D[101010];
Comb<mint, 201010> com;
//---------------------------------------------------------------------------------------------------
mint solve() {
	map<int, int> cnt;
	rep(i, 0, N) cnt[D[i]]++;

	int n = cnt.size();
	rep(i, 0, n) if (cnt[i] == 0) return 0;
	if (cnt[0] != 1) return 0;
	if (D[0] != 0) return 0;

	mint res = 1;
	rep(i, 1, n) res *= mint(cnt[i - 1]) ^ cnt[i];
	return res;
}
//---------------------------------------------------------------------------------------------------
void _main() {
	cin >> N;
	rep(i, 0, N) cin >> D[i];
	cout << solve() << endl;
}



Measured memory_bytes: 6912