#include<bits/stdc++.h>
using namespace std;
const int maxn = 505, mod = 998244353;
int n;
int a[maxn], s[maxn];
int dp[2][maxn][maxn];
int main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i], s[i] = s[i - 1] + a[i];
    for (int i = 1; i <= n; i++)
        if (a[i]) dp[1][i][1] = 1;
    for (int i = 1; i < s[n]; i++) {
        int p = (i & 1);
        for (int j = 0; j <= n; j++)
            for (int k = 0; k <= s[n]; k++)
                dp[p ^ 1][j][k] = 0;
        for (int j = 1; j <= n; j++)
            for (int k = 1; k <= a[j]; k++) {
                if (dp[p][j][k] == 0) continue;
                assert(i <= s[j - 1] + k);
                if (i != s[j - 1] + k) dp[p ^ 1][j][k] = (dp[p ^ 1][j][k] + dp[p][j][k]) % mod;
                if (k != a[j]) dp[p ^ 1][j][k + 1] = (dp[p ^ 1][j][k + 1] + dp[p][j][k]) % mod;
                for (int x = j + 1; x <= n; x++)
                    if (a[x]) dp[p ^ 1][x][1] = (dp[p ^ 1][x][1] + dp[p][j][k]) % mod;
            }
    }
    for (int i = n; i >= 1; i--)
        if (a[i]) {cout << dp[s[n] & 1][i][a[i]] << '\n'; return 0;}
    return 0;
}