output_description: Print the length of the duration (in seconds) in which both Alice and Bob were
  holding down their buttons.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      A B C D
attempt: import sys
  
  a, b, c, d = map(int, input().split(" "))
  box = []
  box.append(a)
  box.append(b)
  box.append(c)
  box.append(d)
  
  
  count = []
  for i in range(a + 1):
      for j in range(b + 1):
          for k in range(c + 1):
              for l in range(d + 1):
                  if c < (b - a):
                      box.sort()
                      p = box[-2]
                      q = box[-3]
                      print(abs(q - p))
                      sys.exit()
                  else:
                      print(0)
                      sys.exit()
  
problem_description: Statement
  
  Alice and Bob are controlling a robot. They each have one switch that controls
  the robot.  
  Alice started holding down her button A second after the start-up of the
  robot, and released her button B second after the start-up.  
  Bob started holding down his button C second after the start-up, and released
  his button D second after the start-up.  
  For how many seconds both Alice and Bob were holding down their buttons?
samples: [{"input": "0 75 25 100", "output": "50\n    \n\nAlice started holding down her button 0 second after the start-up of the\nrobot, and released her button 75 second after the start-up.  \nBob started holding down his button 25 second after the start-up, and released\nhis button 100 second after the start-up.  \nTherefore, the time when both of them were holding down their buttons, is the\n50 seconds from 25 seconds after the start-up to 75 seconds after the start-\nup.\n\n* * *"}, {"input": "0 33 66 99", "output": "0\n    \n\nAlice and Bob were not holding their buttons at the same time, so the answer\nis zero seconds.\n\n* * *"}, {"input": "10 90 20 80", "output": "60"}]