#include <bits/stdc++.h>

#define just return
#define love 0
#define iu ,void();
#define int long long
#define ll int
#define ii inline int
#define gcd __gcd
#define pii pair<int,int>
#define endl '\n'
#define fi first
#define se second
#define unit unsigned int
#define r1 root<<1
#define r2 root<<1|1
#define rt tree[root]
#define rl tree[r1]
#define rr tree[r2]
#define mid ((rt.l+rt.r)>>1)
#define mids ((l+r)>>1)
#define st int root,int l,int r
#define ed int x,int y
#define bit bitset
#define len (rt.r-rt.l+1)
using namespace std;
const int maxn = 1e5 + 5;
const int Max = 2e5 + 5;
const int mod = 998244353;
const int inf = 0x3f3f3f3f3f3f3f;
int dp[505][505], c[505][505];
void solve() {
    int n;
    cin >> n;
    vector<int>a;
    a.push_back(0);
    for (int i = 1;i <= n;i++) {
        int x;
        cin >> x;
        if (x)a.push_back(x);
    }
    int m = n;
    n = a.size() - 1;
    c[0][0] = 1;
    for (int i = 1;i <= m;i++) {
        c[i][0] = c[i][i] = 1;
        for (int j = 1;j < i;j++) {
            c[i][j] = (c[i - 1][j - 1] + c[i - 1][j]) % mod;
        }
    }
    dp[1][a[1] + 1] = 1;
    for (int i = 2;i <= n;i++) {
        for (int j = a[i];j <= m + 1;j++) {
            dp[i][j] = dp[i - 1][j - a[i]];
        }
        for (int j = 2;j <= m + 1;j++) {
            for (int x = 0;x < a[i];x++) {
                for (int k = 1;k < j;k++) {
                    dp[i][x + k + 1] = (dp[i][x + k + 1] + dp[i - 1][j] * c[j - k - 1 + a[i] - x - 1][a[i] - x - 1] % mod) % mod;
                }
            }
        }
    }
    int ans = 0;
    for (int i = 2;i <= m + 1;i++)ans = (ans + dp[n][i]) % mod;
    cout << ans << endl;
}
signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}