#include<bits/stdc++.h>
#define ull unsigned long long
#define ui unsigned int
#define ld long double
#define ll long long
#define lll __int128
#define fi first
#define se second
#define e emplace
#define eb emplace_back
#define db double
#define ef emplace_front
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vi vector<int>
#define vp vector<pii>
#define vt vector<tup>
#define all(x) x.begin(),x.end()
#define mp make_pair

#define FastI
#define FastO
//#define Print
//#define int ll
bool ST,dbg;
static const ll MOD=998244353,Phi=998244352,inv2=499122177,Root=3,iRoot=332748118;
static const ll inf=1073741823,INF=4611686018427387903;
static const ld eps=1e-9,pi=3.1415926535;
char in[1<<20],*p1=in,*p2=in;
char out[1<<20],*p3=out;
using namespace std;
struct tup
{
	int x,y,z;
	tup(int X=0,int Y=0,int Z=0)
	{x=X,y=Y,z=Z;}
	bool operator <(const tup nd)const
	{return x<nd.x;}
};
#ifdef FastI
	#ifdef Print
		#define getchar() ((p1==p2&&(p2=(p1=in)+fread(in,1,1<<20,stdin),p1==p2)?EOF:*p1),(dbg?cerr<<(char)(*p1),0:0),*p1++)
	#else
		#define getchar() (p1==p2&&(p2=(p1=in)+fread(in,1,1<<20,stdin),p1==p2)?EOF:*p1++)
	#endif
#endif

#ifdef FastO
	#define putchar(x) (p3-out==1<<20?fwrite(out,1,1<<20,stdout),p3=out,0:0,*p3++=x)
	#define puts(x) write(x,'\n')
#endif
namespace FastIO
{
	template<typename T> inline void write(T x,char ch=' ')
	{
		if(is_same<char,T>::value)putchar(x);
		else
		{
			if(x<0)x=-x,putchar('-');
			static char st[25];
			int top=0;
			do st[top++]=x%10+'0',x/=10;while(x);
			while(top)putchar(st[--top]);
		}
		ch!='~'?putchar(ch):0;
	}
	inline void write(const char*x,char ch=' ')
	{
		for(int i=0;x[i]!='\0';++i)putchar(x[i]);
		ch!='~'?putchar(ch):0;
	}
	inline void read(char&s){do s=getchar();while(s=='\n'||s==' ');}
	inline void read(char s[])
	{
		int len=0;char st;
		do st=getchar();while(st=='\n'||st==' ');
		s[++len]=st,st=getchar();
		while(st!='\n'&&st!=' '&&st!='\r')s[++len]=st,st=getchar();
		s[++len]='\0';
	}
	template<typename T> inline void read(T &s)
	{
		char ch=getchar();s=0;
		while((ch>'9'||ch<'0')&&ch!='-')ch=getchar();
		bool tf=(ch=='-'&&(ch=getchar()));
		while(ch>='0'&&ch<='9')s=(s<<1)+(s<<3)+ch-'0',ch=getchar();
		s=tf?-s:s;
	}
	inline void edl(){putchar('\n');}
	template<typename T1,typename T2> inline void read(pair<T1,T2> &s){read(s.fi),read(s.se);}
	template<typename T,typename...Args> inline void write(T x,Args...args){write(x,'~'),write(args...);}
	template<typename T,typename...Args> inline void read(T&x,Args&...args){read(x),read(args...);}
	#ifdef FastO
	struct Writer{~Writer(){fwrite(out,1,p3-out,stdout);}}Writ;
	#endif
}
using namespace FastIO;
namespace MTool
{
	inline int Cadd(int a,int b){return (ll)a+b>=MOD?(ll)a+b-MOD:a+b;}
	inline int Cdel(int a,int b){return a-b<0?a-b+MOD:a-b;}
	inline int Cmul(int a,int b){return 1ll*a*b%MOD;}
	inline int sqr(int a){return 1ll*a*a%MOD;}
	inline void Madd(int&a,int b){a=((ll)a+b>=MOD?(ll)a+b-MOD:a+b);}
	inline void Mdel(int&a,int b){a=(a-b<0?a-b+MOD:a-b);}
	inline void Mmul(int&a,int b){a=1ll*a*b%MOD;}
	inline int Cmod(int x){return (x%MOD+MOD)%MOD;}
	inline void Mmod(int&x){x=(x%MOD+MOD)%MOD;}
	template<typename T> inline bool Mmax(T&a,T b){return a<b?a=b,1:0;}
	template<typename T> inline bool Mmin(T&a,T b){return a>b?a=b,1:0;}
	template<typename...Args> inline void Madd(int&a,int b,Args...args){Madd(a,b),Madd(a,args...);}
	template<typename...Args> inline void Mmul(int&a,int b,Args...args){Mmul(a,b),Mmul(a,args...);}
	template<typename...Args> inline void Mdel(int&a,int b,Args...args){Mdel(a,b),Mdel(a,args...);}
	template<typename...Args> inline int Cadd(int a,int b,Args...args){return Cadd(Cadd(a,b),args...);}
	template<typename...Args> inline int Cmul(int a,int b,Args...args){return Cmul(Cmul(a,b),args...);}
	template<typename...Args> inline int Cdel(int a,int b,Args...args){return Cdel(Cdel(a,b),args...);}
	template<typename...Args,typename T> inline bool Mmax(T&a,T b,Args...args){return Mmax(a,b)|Mmax(a,args...);}
	template<typename...Args,typename T> inline bool Mmin(T&a,T b,Args...args){return Mmin(a,b)|Mmin(a,args...);}
	inline int power(int x,int y){int s=1;for(;y;y>>=1,Mmul(x,x))if(y&1)Mmul(s,x);return s;}
}
using namespace MTool;
namespace WrongAnswer_90
{
    const int N=3000000;
    int fr[N+10],inv[N+10];
    inline int C(int n,int m){return m<0||m>n?0:Cmul(fr[n],inv[m],inv[n-m]);}
    inline void init(int n=N)
    {
        fr[0]=inv[0]=1;
        for(int i=1;i<=n;++i)fr[i]=Cmul(fr[i-1],i);
        inv[n]=power(fr[n],MOD-2);
        for(int i=n-1;i>0;--i)inv[i]=Cmul(inv[i+1],i+1);
    }
    inline int calc(int n)
    {return Cdel(C(2*n,n),C(2*n,n-2));}
	int n;
	int a[1000010];
	void mian()
	{
		init();
		read(n);
		int ans=1;
		for(int i=1;i<=n;++i)read(a[i]);
		for(int i=1;i<n;++i)if(a[i]==1)
		return puts("0"),void();
		int lst=0;
		if(a[n]==1)lst=n-1;
		else
		{
			for(int i=n,fl=0;i>=1;fl|=a[i]==3,--i)
			if(fl&&a[i]==2){lst=i;break;}
		}
		int pre=1;
		for(int i=1;i<=lst;++i)
		if(a[i]==2)Mmul(ans,calc(i-pre)),pre=i+1;
		if(a[lst]==3)Mmul(ans,calc(lst-pre+1));
		if(a[n]==1)return write(ans,'\n');
		int tmp=n-lst,tmp2=0,sum=0;
		for(int i=lst+1;i<=n;++i)tmp2+=a[i]==3;
		Madd(sum,Cdel(C(tmp+tmp2,tmp),C(tmp+tmp2,tmp+2)));
		Madd(sum,Cmul(tmp-tmp2,calc(tmp2)));
		write(Cmul(ans,sum),'\n');
	}
	inline void Mian()
	{
		int T=1,C;
//		read(T);
		for(int _T=1;_T<=T;++_T)
		{
//			dbg=_T==1;
			mian();
		}
	}
}
bool ED;
signed main()
{
//	ios::sync_with_stdio(0);
//	freopen("1.in","r",stdin);
//	freopen("1.out","w",stdout);
	WrongAnswer_90::Mian();
	return 0;
}