#include <bits/stdc++.h>
using namespace std;
long long n;
long long a[1006];
long long fac[1000006];
long long power(long long a, long long i) {
  if (i == 0) return 1 % 1000000007;
  long long t = power(a, i / 2);
  long long ans = t * t % 1000000007;
  if (i % 2 == 1) ans = ans * a % 1000000007;
  return ans;
}
long long work(long long m, long long i) {
  return ((fac[m] % 1000000007) *
          (power(fac[i] * fac[m - i] % 1000000007, 1000000007 - 2) %
           1000000007)) %
         1000000007;
}
int main() {
  fac[0] = 1;
  for (int i = 1; i < 1000006; i++) fac[i] = (fac[i - 1] * i) % 1000000007;
  long long ans = 1;
  long long sum = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    sum += a[i];
  }
  for (int i = n; i >= 1; i--) {
    ans = ans * work(sum - 1, a[i] - 1) % 1000000007;
    sum -= a[i];
  }
  cout << ans;
  return 0;
}
