Untitled

def get_user_input():

  n = int(input())
  arr = []
  for i in range(n):
    string = input().strip()
    arr.append(string)
  return arr


def find_max_product(arr):

  max_product = 0
  for i in range(len(arr)):
    for j in range(i + 1, len(arr)):
      product = get_value(arr[i]) * get_value(arr[j])
      max_product = max(max_product, product)
  return max_product


if __name__ == "__main__":
  arr = get_user_input()
  max_product = find_max_product(arr)

  print(max_product)