// start time : 16 : 05

#include <bits/stdc++.h>

#define rep(i,l,r) for (int i = l; i <= r; i++)
#define per(i,r,l) for (int i = r; i >= l; i--)
#define fi first
#define se second
#define pb push_back
#define mp std::make_pair
#define gin std::cin
#define prt std::cout
#define edl std::endl

namespace Main {
  const int N = 505,mod = 998244353;
  int n,a[N],f[N][N],c[N][N];
  void add(int &x,int v) {
    x += v; x %= mod;
  }
  void main() {
    scanf("%d",&n);
    c[0][0] = 1;
    rep(i,1,n) {
      c[i][0] = c[i][i] = 1;
      rep(j,1,i - 1) c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % mod;
    }
    rep(i,1,n) {
      scanf("%d",&a[i]);
    }
    f[n + 1][n + 1] = 1;
    int sum = 0;
    per(i,n + 1,2) {
      sum += a[i];
      rep(j,1,n + 1) {
        rep(k,0,a[i - 1]) {
          if (sum + k > n - j + 1) continue;
          if (k != a[i - 1]) {
            rep(t,1,j - 1) {
              if (j - t >= a[i - 1] - k) {
                add(f[i - 1][t],1ll * c[j - t - 1][a[i - 1] - k - 1] * f[i][j] % mod);
              }
            }
          } else {
            add(f[i - 1][j],f[i][j]);
          }
        }
      }
    }
    int ans = 0;
    rep(i,1,n + 1) add(ans,f[1][i]);
    prt << ans;
  }
} signed main() { Main::main(); return 0; }