#include<bits/stdc++.h>
using namespace std;
const int NN=998244353;
int n;
int b[100100],s[100100],a[100100];
int f[5050][5050],h[5050][5050];
signed main(){
//    freopen("preface.in","r",stdin);
//    freopen("preface.out","w",stdout);
    cin>>n;
    for (int i=1;i<=n;i++)
    cin>>a[i];
    int nn=0;
    for (int i=1;i<=n;i++)
    if(a[i]!=0)b[++nn]=a[i];
    n=nn;//n=1500;
    for (int i=1;i<=n;i++)
    s[i]=s[i-1]+b[i];
    f[1][0]=1;
    for (int i=2;i<=n;i++){
        f[i][0]=1;
        for (int j=0;j<=s[i];j++)
        for (int k=0;k<=b[i];k++)
        h[j][k]=0;
        h[0][0]=1;
        for (int j=1;j<=s[i];j++){
            for (int k=0;k<=b[i];k++)
            h[j][k]=(h[j-1][k]+(k>0?h[j-1][k-1]:0))%NN;
            h[j][0]=(h[j][0]+f[i-1][j])%NN;
        }
        for (int j=1;j<=s[i];j++){
            f[i][j]=f[i-1][j];
            for (int k=0;k<b[i]&&j<s[i]-k;k++){
                int c0=b[i]-1-k;
                f[i][j]=(f[i][j]+h[j-1][c0])%NN;
            }
        }
    }
    int ans=0;
    for (int i=0;i<=s[n];i++)
    ans=(ans+f[n][i])%NN;
    cout<<ans<<"\n";
} //1233