#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rof(i,a,b) for(int i=(a);i>=(b);--i)
using namespace std;
const int Maxn=1e6,Mod=998244353,i2=(Mod+1)/2;

inline int read()
{
    int x=0,f=1;
    char ch=getchar();
    while(ch<'0' || ch>'9')
    {
        if(ch=='-') f=-1;
        ch=getchar();
    }
    while(ch>='0' && ch<='9')
    {
        x=x*10+ch-'0';
        ch=getchar();
    }
    return x*f;
}
inline int Pow(int x,int y)
{
    int res=1;
    while(y)
    {
        if(y&1) res=1ll*res*x%Mod;
        x=1ll*x*x%Mod,y>>=1;
    }
    return res;
}

int n,m,ans,a[Maxn+5],fac[Maxn+5],inv[Maxn+5],f[Maxn+5];
inline int C(int x,int y) {return 1ll*fac[x]*inv[x-y]%Mod*inv[y]%Mod;}

int main()
{
    // freopen("1.in","r",stdin);

    n=read(); fac[0]=inv[0]=1;
    For(i,1,Maxn) fac[i]=1ll*fac[i-1]*i%Mod;
    inv[Maxn]=Pow(fac[Maxn],Mod-2);
    Rof(i,Maxn-1,1) inv[i]=1ll*inv[i+1]*(i+1)%Mod;
    For(i,1,n) a[i]=read(); f[0]=1;
    For(i,1,n-1) f[i]=1ll*f[i-1]*(i*2-1)%Mod;
    For(i,1,n) if(a[i]==1) ans=(ans+1ll*f[i-1]*f[n-i]%Mod*C(n-1,i-1))%Mod;
    cout<<ans<<endl;
    return 0;
}