#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int N = 505;

namespace ModCalculator {
    const int MOD = 998244353;
    inline void Inc(int &x, int y) {
        x += y; if (x >= MOD) x -= MOD;
    }
    inline void Dec(int &x, int y) {
        x -= y; if (x < 0) x += MOD;
    }
    inline int Add(int x, int y) {
        Inc(x, y); return x;
    }
    inline int Sub(int x, int y) {
        Dec(x, y); return x;
    }
    inline int Mul(int x, int y) {
        return 1LL * x * y % MOD;
    }
    inline int Ksm(int x, int y) {
        int ret = 1;
        for (; y; y >>= 1) {
            if (y & 1) ret = Mul(ret, x);
            x = Mul(x, x);
        }
        return ret;
    }
    inline int Inv(int x) {
        return Ksm(x, MOD - 2);
    }
}
using namespace ModCalculator;

int n, a[N], mx, C[N][N], dp[2][N];

void solve() {
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) {
        scanf("%d", &a[i]);
        if (a[i]) mx = i;
    }
    for (int i = 0; i <= 500; ++i) {
        C[i][0] = 1;
        for (int j = 1; j <= i; ++j) {
            C[i][j] = Add(C[i - 1][j], C[i - 1][j - 1]);
        }
    }
    dp[0][0] = 1;
    int pre = 0, cur = 1;
    for (int i = 1, s = 0; i <= n; s += a[i], ++i) {
        if (!a[i]) continue;
        memset(dp[cur], 0, sizeof(dp[cur]));
        for (int j = 0; j <= s; ++j) {
            Inc(dp[cur][j + a[i]], dp[pre][j]);
            for (int x = (i == mx? a[i] : 1); x <= a[i]; ++x) {
                for (int y = 0; y <= j; ++y) {
                    Inc(dp[cur][j - y + a[i] - x], Mul(dp[pre][j], C[x - 1 + y][y]));
                }
            }
        }
        swap(pre, cur);
    }
    printf("%d\n", dp[pre][0]);
}

int main() {
    solve();
    return 0;
}