def main():
  from sys import stdin
  import math
  readline=stdin.readline
  n = int(readline())
  A = list(map(int, readline().split()))
  mod = 10**9 + 7
  ans = 1
  for a in A:
    if a == 0:
      print(-1)
      exit()
    if a >= 4:
      print(mod)
      exit()
    ans *= pow(a,math.factorial(a))
  print(mod % ans)
main()