#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, U b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
template <class T, class T1>
inline void print(T first, T1 second) {
  printsp(first), println(second);
}
template <class T, class T1, class T2>
inline void print(T first, T1 second, T2 z) {
  printsp(first), printsp(second), println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
int n, con[1010][1010], dp[1010], a[1010], sum[1010];
void proc() {
  con[0][0] = 1;
  for (int i = 1; i < 1010; i++) {
    con[i][0] = 1;
    con[i][i] = 1;
    for (int j = 1; j < i; j++)
      con[i][j] =
          (con[i - 1][j - 1] % 1000000007 + con[i - 1][j] % 1000000007) %
          1000000007;
  }
}
int main() {
  proc();
  gn(n);
  for (int i = 1; i <= n; i++) {
    gn(a[i]);
    sum[i] = sum[i - 1] + a[i];
  }
  dp[1] = 1;
  for (int i = 2; i <= n; i++)
    dp[i] = (long long)dp[i - 1] * (con[sum[i] - 1][a[i] - 1]) % 1000000007;
  println(dp[n]);
  return 0;
}
