#include <bits/stdc++.h>
using namespace std;
int MOD = 1000000007;
int dp[1001][1001];
int main() {
  int k;
  cin >> k;
  int balls[1000];
  int n = 0;
  for (int i = 0; i < k; i++) {
    cin >> balls[i];
    n += balls[i];
  }
  long long l = 1;
  for (int i = 0; i <= n; i++) {
    dp[i][0] = 1;
    dp[i][i] = 1;
    for (int j = 1; j <= i; j++) {
      dp[i][j] = (dp[i - 1][j] + dp[i - 1][j - 1]) % MOD;
    }
  }
  long long ans = 1;
  int cur = balls[0];
  for (int i = 1; i < k; i++) {
    cur += balls[i];
    ans = ((ans % MOD) * (dp[cur - 1][balls[i] - 1]) % MOD) % MOD;
  }
  cout << ans << endl;
  return 0;
}
