#include <bits/stdc++.h>
using namespace std;
long long n;
long long a[1005];
long long fac[1000005];
long long ppow(long long a, long long b) {
  long long c = 1;
  while (b) {
    if (b & 1) c = c * a % 1000000007;
    a = a * a % 1000000007;
    b >>= 1;
  }
  return c;
}
long long work(long long m, long long i) {
  return ((fac[m] % 1000000007) *
          (ppow((fac[i] * fac[m - i]) % 1000000007, 1000000007 - 2) %
           1000000007)) %
         1000000007;
}
int main() {
  long long i, j, k;
  fac[0] = 1;
  for (int i = 1; i < 1000005; i++) {
    fac[i] = (fac[i - 1] * i) % 1000000007;
  }
  long long ans = 1, 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 *= work(sum - 1, a[i] - 1);
    ans %= 1000000007;
    sum -= a[i];
  }
  cout << ans << endl;
}
