output_description: Print the answer.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      a b c d
attempt: a, b, c, d = [int(x) for x in input().split()]
  
  max_x = b
  max_y = d
  min_x = a
  min_y = c
  
  li_1 = [max_x, min_x]
  li_2 = [max_y, min_y]
  max_num = -(10**9)
  for i in li_1:
      for j in li_2:
          num = i * j
          if num > max_num:
              max_num = num
  
  print(max_num)
  
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"}]