#include <bits/stdc++.h>
using namespace std;
namespace IO {
const int sz = 1 << 20;
char a[sz + 5], b[sz + 5], *p1 = a, *p2 = a, *t = b, p[105];
inline char gc() {
  return getchar();
  if (p1 == p2) p2 = (p1 = a) + fread(a, 1, sz, stdin);
  return *p1++;
}
template <class T>
inline T read() {
  T ret = 0;
  char c = gc();
  int f = 1;
  for (; c < '0' || c > '9'; c = gc())
    if (c == '-') f = -1;
  for (; c >= '0' && c <= '9'; c = gc()) ret = ret * 10 + (c - '0');
  return ret * f;
}
template <class T>
inline void read(T& ret) {
  ret = read<T>();
}
inline void flush() { fwrite(b, 1, t - b, stdout), t = b; }
inline void pc(char x) {
  *t++ = x;
  if (t - b == sz) flush();
}
template <class T>
inline void print(T x, char c = '\n') {
  if (x < 0) x = -x, pc('-');
  if (x == 0) pc('0');
  int t = 0;
  for (; x; x /= 10) p[++t] = x % 10 + '0';
  for (; t; --t) pc(p[t]);
  pc(c);
}
struct F {
  ~F() { flush(); }
} f;
}  // namespace IO
using IO::print;
using IO::read;
const int mo = 1e9 + 7;
inline int add(int a, int b) { return a + b < mo ? a + b : a + b - mo; }
inline int dec(int a, int b) { return a < b ? a + mo - b : a - b; }
inline int mul(int a, int b) { return 1LL * a * b % mo; }
const int N = 1e3 + 10;
int k;
int c[N], s[N];
int C[N][N];
int f[N];
int main() {
  for (int i = 0; i <= 1000; i++) C[i][0] = C[0][i] = 1;
  C[0][0] = 0;
  for (int i = 1; i <= 1000; i++)
    for (int j = 1; j <= 1000; j++) C[i][j] = add(C[i - 1][j], C[i][j - 1]);
  read(k);
  for (int i = 1; i <= k; read(c[i]), s[i] = add(s[i - 1], c[i]), i++)
    ;
  f[1] = 1;
  for (int i = 2; i <= k; i++) f[i] = mul(f[i - 1], C[s[i - 1]][c[i] - 1]);
  print(f[k]);
  return 0;
}
