#include<bits/stdc++.h>
using namespace std;
using ll=long long;
// using ll=long double;
using pii=pair<ll,ll>;
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
const int N = 510, mod = 998244353;
ll f[N][N];
ll a[N];
ll len[N]; 
ll c[N][N];
ll sumc[N][N];
void init()
{
    for(int i=0;i<=500;i++)
    {
        for(int j=0;j<=i;j++)
        {
            if(!j) c[i][j] = 1;
            else c[i][j] = (c[i-1][j-1] + c[i-1][j])%mod;
        }
    }
    for(int i=0;i<=500;i++)
    {
        for(int j=0;j<=i;j++)
        {
            if(!j) sumc[i][j] = c[i][j];
            else sumc[i][j] = (sumc[i][j-1] + c[i][j])%mod;
        }
    }
}
void solve()
{
    ll n;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i], len[i] = len[i-1] + a[i];
	int flag = 1;
	f[0][0] = 1;
    for(int i=1;i<=n;i++)
    {
    	if(flag) 
    	{
    		f[i][0] = 1;
    		if(len[i]) flag = 0;
    		continue;
		}
        for(int j =0;j<len[i-1];j++)
        {
            f[i][j] += f[i-1][j];
            if(a[i] == 0) continue;
            for(int k=j+1; k<len[i]; k++)
            {
                if(k-j<=a[i] && k-j-1 <= len[i-1]-j-1) 
                {               
                    f[i][k] += f[i-1][j] * sumc[k-j-1][k-j-1]%mod;
                    f[i][k]%=mod;
                }
                else if(k-j>a[i] && k-j-1<=len[i-1]-j-1)
                {
//                	cout<<11111<<endl;
                    ll dlt = (k-j) - a[i];
                    f[i][k] += f[i-1][j] * (sumc[k-j-1][k-j-1] - sumc[k-j-1][dlt-1])%mod;
                    f[i][k]%=mod;
                    f[i][k] = (f[i][k] + mod)%mod;
                }
                else if(k-j<=a[i] && k-j-1>len[i-1]-j-1)
                {
                    ll dlt = (k-j-1) - (len[i-1] - j-1);
                    
                    f[i][k] += f[i-1][j] * sumc[k-j-1][k-j-1-dlt]%mod;
                    f[i][k]%=mod;
                }
                else 
                {
                    ll dlt1 = (k-j) - a[i];
                    ll dlt2 = (k-j-1) - (len[i-1] - j-1);
                    if(dlt1 >= k-j-dlt2) continue;
                    f[i][k] += f[i-1][j] * (sumc[k-j-1][k-j-1-dlt2] - sumc[k-j-1][dlt1-1])%mod;
                    f[i][k]%=mod;
                    f[i][k] = (f[i][k] + mod)%mod;
                }
            }
        }
    }
    ll ans = 0;
//    cout<<f[2][0]<<' '<<f[2][1]<<' '<<f[2][2]<<' '<<f[2][3]<<endl;
    for(int i=0;i<=500;i++)
    {
        ans = (ans + f[n][i])%mod;
    }
    cout<<ans;
}

int main(){
    IOS;
    int t=1;
    init();
    // cin>>t;
    while(t--) solve();
    return 0;
}