#include <bits/stdc++.h>
#define N 1000011
using namespace std;
int n,fac[N],ifac[N],ffac[N],a[N];const int p=998244353;
inline int qpow(int bs,int ex){int ans=1;while(ex){if(ex&1)ans=1ll*ans*bs%p;ex>>=1;bs=1ll*bs*bs%p;}return ans;}
int main()
{
	scanf("%d",&n);for(int i=1;i<=n;++i)scanf("%d",a+i);
	fac[0]=1;for(int i=1;i<N;++i)fac[i]=1ll*fac[i-1]*i%p;
	ifac[N-1]=qpow(fac[N-1],p-2);for(int i=N-2;~i;--i)ifac[i]=1ll*ifac[i+1]*(i+1)%p;
	ffac[0]=1;for(int i=1;i<N;++i)ffac[i]=1ll*ffac[i-1]*(2*i-1)%p;
	int ans=0;
	for(int i=1;i<=n;++i)if(a[i])
	{
		ans=(ans+1ll*ffac[i-1]*ffac[n-i]%p*fac[n-1]%p*ifac[i-1]%p*ifac[n-i])%p;
	}
	printf("%d\n",ans);
	fclose(stdin);fclose(stdout);return 0;
}