#include <bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for (int i=a; i<b; i++)
#define trav(a,b) for (auto a : b)
#define all(x) begin(x),end(x)
#define lld long long
const lld MOD=998244353;
using i64 = long long;

lld DP[1000][1000];

void solve() {
	int n;
	cin>>n;
	vector<int> arr;
	rep(i,0,n){
		int x;
		cin>>x;
		rep(k,0,x)arr.push_back(i);
	}
	n=arr.size();
	rep(i,0,n+1){
		rep(j,0,n+1)DP[i][j]=0;
	}
	DP[0][0]=1;
	rep(i,0,n+1){
		for(int j=n;j>-1;j--){
			if(j>0){
				DP[i][j-1]+=DP[i][j];
				DP[i][j-1]%=MOD;
			}
			rep(k,i+1,n+1){
				if(k==i+1 || arr[k-1]>arr[k-2])DP[k][j+(k-i-1)]+=DP[i][j],DP[k][j+(k-i-1)]%=MOD;
			}
		}
	}
	//rep(i,0,n+1){
		//rep(j,0,n+1){
			//cout<<DP[i][j]<<" ";
		//}cout<<endl;
	//}
	cout<<DP[n][0]<<"\n";
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int tt = 1;
	//cin >> tt;
	while (tt--) solve();
	return 0;
}