// Slower C++ solution:
#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;

}




// Faster C++ solution for the same problem (measured speedup: 4.474676385194833x):
#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;

}

typedef ModInt<998244353> mint;

/*---------------------------------------------------------------------------------------------------

　　　　　　　　　　　 ∧＿∧

　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!

　　　　 （ ´_ゝ`）　/　 ⌒i     @hamayanhamayan

　　　　／　　　＼　 　  |　|

　　　 /　　 /￣￣￣￣/　　|

　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿

　 　　　＼/＿＿＿＿/　（u　⊃

---------------------------------------------------------------------------------------------------*/























int N, D[101010];

//---------------------------------------------------------------------------------------------------

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;

}