import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string rstring(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T rtype(T)(){ return rstring.to!T; } alias rint = rtype!int, rlong = rtype!long, rreal = rtype!real;
T[] rtypes(T)(int n){ return n.iota.map!(i => rtype!T()).array; } alias rint = rtypes!int, rlong = rtypes!long, rreal = rtypes!real;
T[][] rtypess(T)(int n, int m){ return n.iota.map!(i => rtypes!T(m)).array; } alias rint = rtypess!int, rlong = rtypess!long, rreal = rtypess!real;

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

void solve(){
	int n = rint;
	int[] ds = rint(n);
	
	if(ds[0] != 0){
		"0".writeln;
		return;
	}
	
	int[int] dcnt;
	int dmax = -1;
	foreach(d; ds){
		if(d !in dcnt) dcnt[d] = 0;
		dcnt[d] += 1;
		dmax = max(dmax, d);
	}
	
	if(dcnt[0] != 1){
		"0".writeln;
		return;
	}
	
	log("dcnt:", dcnt);
	log("dmax:", dmax);
	
	Finite ans = 1;
	int last = 1;
	foreach(d; 1 .. dmax + 1){
		log("last:", last, "d:", d, "dcnt:", dcnt[d]);
		if(d !in dcnt){
			"0".writeln;
			return;
		}
		ans *= pow(last, dcnt[d]);
		last = dcnt[d];
	}
	
	ans.writeln;
}

import std.conv;
struct Finite{
	ulong value; static ulong mod = 998244353;
	private static ulong[] _inv = [0, 1], _frac = [1, 1], _invfrac = [1, 1];
	this(ulong v){ value = v % mod; }
	bool opCast(T: bool)(){ return value != 0; }
	Finite opUnary(string s){ ulong v;
		if(s == "+") v = value;
		else if(s == "-") v = mod - value;
		else if(s == "++") v = value + 1;
		else if(s == "--") v = value + mod - 1;
		else assert(0, "Operator unary " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opBinary(string s)(Finite b){
		return opBinary!s(b.value);
	}
	Finite opBinary(string s)(ulong u){ ulong v;
		if(s == "+") v = value + u;
		else if(s == "-") v = value + mod - u;
		else if(s == "*") v = value * u;
		else if(s == "/") v = value * inv(u);
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opBinaryRight(string s)(ulong u){ ulong v;
		if(s == "+") v = u + value;
		else if(s == "-") v = u + mod - value;
		else if(s == "*") v = u * value;
		else if(s == "/") v = u * invvalue;
		else assert(0, "Operator " ~ s ~ " not implemented");
		return Finite(v);
	}
	Finite opAssign(ulong v){ value = v; return this; }
	Finite opOpAssign(string s)(Finite b){
		return opOpAssign!s(b.value);
	}
	Finite opOpAssign(string s)(ulong v){
		if(s == "+") value = (value + v) % mod;
		else if(s == "-") value = (value + mod - v) % mod;
		else if(s == "*") value = (value * v) % mod;
		else if(s == "/") value = (value * inv(v)) % mod;
		else assert(0, "Operator " ~ s ~ "= not implemented");
		return this;
	}
	bool opEquals(Finite b){
		return(value == b.value);
	}
	string toString(){ return value.to!string; }
	ulong inv(ulong v){
		assert(v > 0);
		assert(v < mod);
		while(v >= _inv.length){
			_inv ~= _inv[mod % $] * (mod - mod / _inv.length) % mod;
		}
		return _inv[v];
	}
	ulong invvalue(){
		return inv(value);
	}
	static Finite opCall(ulong v){
		return Finite(v);
	}
	
}

Finite pow(long a, int n){
 static Finite[][long] _pow;
 if(a !in _pow) _pow[a] = [Finite(1)];
 while(n > _pow[a].length - 1){
	 log("a:", a, "pow:", _pow[a]);
	 _pow[a] ~= _pow[a][$ - 1] * a;
 }
 return _pow[a][n];
}

Finite pow(Finite a, int n){
 return pow(a.value, n);
}


Measured memory_bytes: 9148