output_description: Print the answer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      a b c d
attempt: x = input().split(" ")
  a = int(x[0])
  b = int(x[1])
  c = int(x[2])
  d = int(x[3])
  ab = a + b
  cd = c + d
  con1 = a >= -10**9 and a <= b and b <= 10**9
  con2 = c >= -10**9 and c <= d and d <= 10**9
  def positive(a, b, c, d):
      if a >= b and c >= d:
          return a * c
      elif a >= b and c <= d:
          return a * d
      elif a <= b and c >= d:
          return b * c
      else:
          return b * d
  def negativeLeft(a, b, c, d):
      if a >= b and c >= d:
          return a * d
      elif a >= b and c <= d:
          return a * c
      elif a <= b and c >= d:
          return b * d
      else:
          return b * c
  def negativeRight(a, b, c, d):
      if a >= b and c >= d:
          return b * c
      elif a >= b and c <= d:
          return b * d
      elif a <= b and c >= d:
          return a * c
      else:
          return a * d
  def negative(a, b, c, d):
      if a >= b and c >= d:
          return b * d
      elif a >= b and c <= d:
          return b * c
      elif a <= b and c >= d:
          return a * d
      else:
          return a * c
  if con1 == True and con2 == True:
      if ab >= 0 and cd >= 0:
          print(positive(a, b, c, d))
      elif ab >= 0 and cd <= 0:
          print(negativeRight(a, b, c, d))
      elif ab <= 0 and cd >= 0:
          print(negativeLeft(a, b, c, d))
      else:
          print(negative(a, b, c, d))
  else:
      print()
  
problem_description: Statement
  
  Given are integers a,b,c and d. If x and y are integers and a \leq x \leq b
  and c\leq y \leq d hold, what is the maximum possible value of x \times y?
samples: [{"input": "1 2 1 1", "output": "2\n    \n\nIf x = 1 and y = 1 then x \\times y = 1. If x = 2 and y = 1 then x \\times y =\n2. Therefore, the answer is 2.\n\n* * *"}, {"input": "3 5 -4 -2", "output": "-6\n    \n\nThe answer can be negative.\n\n* * *"}, {"input": "-1000000000 0 -1000000000 0", "output": "1000000000000000000"}]