#include <bits/stdc++.h>
using namespace std;
template <class C>
void mini(C& a4, C b4) {
  a4 = min(a4, b4);
}
template <class C>
void maxi(C& a4, C b4) {
  a4 = max(a4, b4);
}
template <class T1, class T2>
ostream& operator<<(ostream& out, pair<T1, T2> pair) {
  return out << "(" << pair.first << ", " << pair.second << ")";
}
template <class A, class B, class C>
struct Triple {
  A first;
  B second;
  C third;
  bool operator<(const Triple& t) const {
    if (first != t.first) return first < t.first;
    if (second != t.second) return second < t.second;
    return third < t.third;
  }
};
template <class T>
void ResizeVec(T&, vector<long long>) {}
template <class T>
void ResizeVec(vector<T>& vec, vector<long long> sz) {
  vec.resize(sz[0]);
  sz.erase(sz.begin());
  if (sz.empty()) {
    return;
  }
  for (T& v : vec) {
    ResizeVec(v, sz);
  }
}
template <class A, class B, class C>
ostream& operator<<(ostream& out, Triple<A, B, C> t) {
  return out << "(" << t.first << ", " << t.second << ", " << t.third << ")";
}
struct FastNewton {
 private:
  long long P;
  long long range;
  vector<long long> inv;
  vector<long long> fact;
  vector<long long> fact_inv;
  vector<long long> v_p;

 public:
  FastNewton(long long _P, long long _range = 0) { init(_P, _range); }
  void init(long long _P, long long _range = -1) {
    P = _P;
    if (_range == -1) {
      range = P;
    } else {
      range = _range;
    }
    inv.resize(range + 5);
    fact.resize(range + 5);
    fact_inv.resize(range + 5);
    v_p.resize(range + 5);
    fact[0] = 1;
    fact_inv[0] = 1;
    inv[0] = -1;
    inv[1] = 1;
    for (long long i = 2; i < min(range, P); i++) {
      inv[i] = P - (P / i) * inv[P % i] % P;
    }
    for (long long i = 1; i <= range; i++) {
      long long tmp = i;
      while (tmp % P == 0) {
        tmp /= P;
      }
      fact[i] = tmp * fact[i - 1] % P;
      fact_inv[i] = fact_inv[i - 1] * inv[tmp] % P;
    }
    for (long long i = 1; i <= range; i++) {
      v_p[i] = i / P + v_p[i / P];
    }
  }
  long long get_inv(long long a) const {
    if (a % P == 0) {
      cout << "ERROR: 0 has not got its inverse\n";
      return -1;
    }
    return inv[a % P];
  }
  long long get_normal_fact(long long n) const {
    if (n >= P) {
      return 0;
    }
    return fact[n];
  }
  long long get_better_fact(long long n) const {
    if (n > range) {
      cout << "ERROR: n too large\n";
      return -1;
    }
    return fact[n];
  }
  long long get_v_p(long long n) const {
    if (n > range) {
      cout << "ERROR: n too large\n";
      return -1;
    }
    return v_p[n];
  }
  long long choose(long long n, long long k) const {
    if (k < 0 || k > n) {
      return 0;
    }
    if (v_p[n] == v_p[k] + v_p[n - k]) {
      return fact[n] * fact_inv[k] % P * fact_inv[n - k] % P;
    } else {
      return 0;
    }
  }
};
const long long P = 1e9 + 7;
const long long N = 2e6 + 6;
long long c[N];
int main() {
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  if (0) cout << fixed << setprecision(10);
  cin.tie(0);
  double beg_clock = 1.0 * clock() / CLOCKS_PER_SEC;
  FastNewton newt(P, N);
  long long res = 1;
  long long sum = 0;
  long long k;
  cin >> k;
  ;
  for (long long i = (1); i <= (k); ++i) {
    cin >> c[i];
    res = res * newt.choose(sum + c[i] - 1, c[i] - 1) % P;
    sum += c[i];
  }
  cout << res << endl;
  return 0;
}
