#include <bits/stdc++.h>

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define RITR(x,c) for(__typeof(c.rbegin()) x=c.rbegin();x!=c.rend();x++)
#define setp(n) fixed << setprecision(n)

#define lf double
#define ll long long
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll,ll>
#define pi pair<int,int>

#define all(a) (a.begin()),(a.end())
#define rall(a) (a.rbegin()),(a.rend())
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define ins insert

using namespace std;

template<::std::uint_fast64_t mod>
class ModInt{
private:
	using value_type = ::std::uint_fast64_t;
	value_type n;
public:
	ModInt() : n(0) {}
	ModInt(value_type n_) : n(n_ % mod) {}
	ModInt(const ModInt& m) : n(m.n) {}

	template<typename T>
	explicit operator T() const { return static_cast<T>(n); }
	value_type get() const { return n; }

	friend ::std::ostream& operator<<(::std::ostream &os, const ModInt<mod> &a) {
		return os << a.n;
	}

	friend ::std::istream& operator>>(::std::istream &is, ModInt<mod> &a) {
		value_type x;
		is >> x;
		a = ModInt<mod>(x);
		return is;
	}

	bool operator==(const ModInt& m) const { return n == m.n; }
	bool operator!=(const ModInt& m) const { return n != m.n; }
	ModInt& operator*=(const ModInt& m){ n = n * m.n % mod; return *this; }

	ModInt pow(value_type b) const{
		ModInt ans = 1, m = ModInt(*this);
		while(b){
			if(b & 1) ans *= m;
			m *= m;
			b >>= 1;
		}
		return ans;
	}

	ModInt inv() const { return (*this).pow(mod-2); }
	ModInt& operator+=(const ModInt& m){ n += m.n; n = (n < mod ? n : n - mod); return *this; }
	ModInt& operator-=(const ModInt& m){ n += mod - m.n; n = (n < mod ? n : n - mod); return *this; }
	ModInt& operator/=(const ModInt& m){ *this *= m.inv(); return *this; }
	ModInt operator+(const ModInt& m) const { return ModInt(*this) += m; }
	ModInt operator-(const ModInt& m) const { return ModInt(*this) -= m; }
	ModInt operator*(const ModInt& m) const { return ModInt(*this) *= m; }
	ModInt operator/(const ModInt& m) const { return ModInt(*this) /= m; }
	ModInt& operator++(){ n += 1; return *this; }
	ModInt& operator--(){ n -= 1; return *this; }
	ModInt operator++(int){
		ModInt old(n);
		n += 1;
		return old;
	}
	ModInt operator--(int){
		ModInt old(n);
		n -= 1;
		return old;
	}
	ModInt operator-() const { return ModInt(mod-n); }
};

template<::std::uint_fast64_t mod>
class Combination
{
private:
	::std::vector<ModInt<mod> > _fact;
	::std::vector<ModInt<mod> > _finv;
public:
	Combination(int range){
		_fact.resize(range+1);
		_finv.resize(range+1);
		_fact[0] = _fact[1] = 1;
		_finv[0] = _finv[1] = 1;
		for(int i=2; i<=range; i++){
			_fact[i] = _fact[i-1]*i;
			_finv[i] = _fact[i].inv();
		}
	}

	ModInt<mod> fact(int x){return _fact[x];}
	ModInt<mod> finv(int x){return _finv[x];}
	ModInt<mod> comb(int x, int y){
		return _fact[x]*_finv[y]*_finv[x-y];
	}
	ModInt<mod> homo(int x, int y){
		return comb(x+y-1, y);
	}
};

const ll MOD = 998244353;

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	ll n; cin>>n;
	vll M(n, 0);
	rep(i, n){
		ll d; cin>>d;
		if ((d!=0 && i==0)||(d==0 && i!=0)){
			cout << "0\n";
			return 0;
		}
		M[d]++;
	}
	ModInt<MOD> ans(1);
	for(int i=1; i<n; i++){
		ModInt<MOD> temp(M[i-1]);
		ans *= temp.pow(M[i]);
	}
	cout << ans << endl;
	return 0;
}

Measured memory_bytes: 1024