//Let's join Kaede Takagaki Fan Club !!
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cassert>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <functional>
#include <iostream>
#include <map>
#include <set>
//#include <unordered_map>
//#include <unordered_set>
#include <cassert>
#include <iomanip>
#include <chrono>
#include <random>
#include <bitset>
#include <complex>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#include <atcoder/convolution>
//#include <atcoder/lazysegtree>
//#include <atcoder/maxflow>
//#include <atcoder/mincostflow>
//#include <atcoder/segtree>
//#include <atcoder/string>
using namespace std;
//using namespace atcoder;
#define int long long
//#define L __int128
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
#define pu push
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define a first
#define b second
#define fi first
#define sc second
#define rng(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,x) for(int i=0;i<x;i++)
#define gnr(i,a,b) for(int i=(int)(b)-1;i>=(int)(a);i--)
#define per(i,b) gnr(i,0,b)
#define repn(i,x) for(int i=1;i<=x;i++)
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
#define all(x) x.begin(),x.end()
#define si(x) (int)(x.size())
#define pcnt(x) __builtin_popcountll(x)
#define all(x) x.begin(),x.end()

#ifdef LOCAL
#define dmp(x) cerr<<__LINE__<<" "<<#x<<" "<<x<<endl
#else
#define dmp(x) void(0)
#endif
 
template<class t,class u> bool chmax(t&a,u b){if(a<b){a=b;return true;}else return false;}
template<class t,class u> bool chmin(t&a,u b){if(b<a){a=b;return true;}else return false;}
 
template<class t> using vc=vector<t>;
 
template<class t,class u>
ostream& operator<<(ostream& os,const pair<t,u>& p){
	return os<<"{"<<p.fi<<","<<p.sc<<"}";
}
 
template<class t> ostream& operator<<(ostream& os,const vc<t>& v){
	os<<"{";
	for(auto e:v)os<<e<<",";
	return os<<"}";
}
 
 //https://codeforces.com/blog/entry/62393
struct custom_hash {
	static uint64_t splitmix64(uint64_t x) {
		// http://xorshift.di.unimi.it/splitmix64.c
		x += 0x9e3779b97f4a7c15;
		x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
		x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
		return x ^ (x >> 31);
	}
 
	size_t operator()(uint64_t x) const {
		static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
		return splitmix64(x + FIXED_RANDOM);
	}
	//don't make x negative!
	size_t operator()(pair<int,int> x)const{
		return operator()(uint64_t(x.first)<<32|x.second);
	}
};
//unordered_set -> dtype, null_type
//unordered_map -> dtype(key), dtype(value)
using namespace __gnu_pbds;
template<class t,class u>
using hash_table=gp_hash_table<t,u,custom_hash>;

template<class T>
void o(const T &a,bool space=false){
	cout << a << (space?' ':'\n');
}
//ios::sync_with_stdio(false);
const ll mod = 998244353;
//const ll mod = 1000000007;
mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());

struct modular{
	ll v;
	modular(ll vv=0){s(vv%mod+mod);}
	modular& s(ll vv){
		v=vv<mod?vv:vv-mod;
		return *this;
	}
	modular operator-()const{return modular()-*this;}
	modular &operator+=(const modular&rhs){return s(v+rhs.v);}
	modular &operator-=(const modular&rhs){return s(v+mod-rhs.v);}
	modular &operator*=(const modular&rhs){v=ll(v)*rhs.v%mod;return *this;}
	modular &operator/=(const modular&rhs){return *this*=rhs.inv();}
	modular operator+(const modular&rhs)const{return modular(*this)+=rhs;}
	modular operator-(const modular&rhs)const{return modular(*this)-=rhs;}
	modular operator*(const modular&rhs)const{return modular(*this)*=rhs;}
	modular operator/(const modular&rhs)const{return modular(*this)/=rhs;}
	modular pow(ll n)const{
		if(n<0)return inv().pow(-n);
		modular res(1),x(*this);
		while(n){
			if(n&1)res*=x;
			x*=x;
			n>>=1;
		}
		return res;
	}
	modular inv()const{return pow(mod-2);}
	friend modular operator+(ll x,const modular&y){
		return modular(x)+y;
	}
	friend modular operator-(ll x,const modular&y){
		return modular(x)-y;
	}
	friend modular operator*(ll x,const modular&y){
		return modular(x)*y;
	}
	friend modular operator/(ll x,const modular&y){
		return modular(x)/y;
	}
	friend ostream& operator<<(ostream&os,const modular&m){
		return os<<m.v;
	}
	friend istream& operator>>(istream&is,modular&m){
		ll x;is>>x;
		m=modular(x);
		return is;
	}
	bool operator<(const modular&r)const{return v<r.v;}
	bool operator==(const modular&r)const{return v==r.v;}
	bool operator!=(const modular&r)const{return v!=r.v;}
	explicit operator bool()const{
		return v;
	}
};
ll modpow(ll x,ll n){
	ll res=1;
	while(n>0){
		if(n&1) res=res*x%mod;
		x=x*x%mod;
		n>>=1;
	}
	return res;
}
#define _sz 1000005
modular F[_sz],R[_sz];
void make(){
	F[0] = 1;
	for(int i=1;i<_sz;i++) F[i] = F[i-1] * i;
	R[_sz-1] = F[_sz-1].pow(mod-2);
	for(int i=_sz-2;i>=0;i--) R[i] = R[i+1] * (i+1);
}
modular C(int a,int b){
	if(b < 0 || a < b) return modular();
	return F[a]*R[b]*R[a-b];
}
using ld=long double;
using vi=vc<int>;
using ull=unsigned long long;
/*int dst(P p, P q){
	return (p.a-q.a)*(p.a-q.a)+(p.b-q.b)*(p.b-q.b);
}*/
/*template<class t>
void add_inplace(t &a, t b){
	if(a.size() < b.size()) swap(a, b);
	for(int i=0;i<b.size();i++){
		a[i] += b[i];
		if(a[i] < 0) a[i] += mod;
		if(a[i] >= mod) a[i] -= mod;
	}
	return ;
}*/
/*template<class t>
void ov(const vc<t>&a){
	if(a.empty()) return;
	rep(i, a.size()) cout << a[i] << (i+1==a.size()?'\n':' ');
}*/
//o(ans?"Yes":"No");

pair<int,modular> count_bubble(vc<int>vec){
	int n=si(vec);
	int sum=0,ret1=0;
	rep(i,n){
		if(vec[i])sum++;
		else ret1+=sum;
	}
	if(!ret1) return mp(0, modular(1));
	
	vc<vc<int>>ri(n+1, vc<int>(n+1, 0));
	vc<vc<int>>dw(n+1, vc<int>(n+1, 0));
	vc<int>bot(n+1, -1);
	P now=mp(0, 0);
	rep(i, n){
		if(vec[i]==0) now.b++;
		else{
			bot[now.a++] = now.b;
		}
	}
	modular ret2=F[ret1];
	for(int x=now.a-1;x>=0;x--){
		for(int y=0;y<now.b;y++){
			if(bot[x] == -1) continue;
			if(bot[x] > y) continue;
			dw[x][y] = 1+(!y?0:dw[x][y-1]);
			ri[x][y] = 1+ri[x+1][y];
			ret2 /= (dw[x][y]+ri[x][y]-1);
		}
	}
	return mp(ret1, ret2);
}
void solve(){
	int n;
	cin>>n;
	vc<int>a(n);
	int sum=0;
	rep(i, n) cin >> a[i];
	reverse(all(a));
	rep(i, n) sum+=a[i];
	if(sum&1){
		o(0);
		return;
	}
	vc<int>ret{1};
	repn(i, n-1){
		rep(j, a[i-1]-a[i]){
			ret.pb(0);
		}
		ret.pb(1);
	}
	rep(j, a[n-1]) ret.pb(0);
	vc<int>odd, even;
	int sumodd=0;
	rep(i, ret.size()){
		if(i&1){
			odd.pb(ret[i]);
			sumodd-=ret[i];
		}
		else even.pb(ret[i]);
	}
	SORT(ret);
	rep(i, ret.size()){
		if(i&1) sumodd+=ret[i];
	}
	if(sumodd){
		o(0);
		return;
	}
	make();
	auto a1 = count_bubble(odd);
	auto a2 = count_bubble(even);
	o( a1.b*a2.b*C(a1.a+a2.a, a1.a));
}
signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	int t; t = 1; //cin >> t;
	while(t--) solve();
}