#include<bits/stdc++.h>
using namespace std;
#define int long long
constexpr int mod=998244353;

int a[510],sum[510],f[510][510],n,m;
signed main(){
  cin>>n;
  for(int i=1;i<=n;++i)cin>>a[i],sum[i]=sum[i-1]+a[i],m+=a[i];
  for(int i=1;i<=n;++i)if(a[i])f[1][i]=1;
  for(int i=2;i<=m;++i){
    for(int j=1;j<=n;++j){
      for(int k=j;k<=n;++k){
        if(!a[k])continue;
        if(k==j&&i>sum[j])continue;
        f[i][k]=(f[i][k]+f[i-1][j])%mod;
      }
    }
  }
  //for(int i=1;i<=m;++i)for(int j=1;j<=n;++j)cout<<i<<' '<<j<<' '<<f[i][j]<<endl;
  cout<<f[m][n];
  return 0;
}