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: def inputs(num_of_input):
      ins = [input() for i in range(num_of_input)]
      return ins
  
  
  def solve(inputs):
      i = inputs[0].split()
      times = {"a": {}, "b": {}}
      times["a"]["start"] = int(i[0])
      times["a"]["end"] = int(i[1])
      times["b"]["start"] = int(i[2])
      times["b"]["end"] = int(i[3])
  
      first_start = "a" if times["a"]["start"] < times["b"]["start"] else "b"
      second_start = "b" if first_start == "a" else "a"
  
      first_end = "a" if times["a"]["end"] < times["b"]["end"] else "b"
      second_end = "b" if first_end == "a" else "a"
  
      if second_start == first_end:
          return times[first_end]["end"] - times[second_start]["start"]
      if times[first_end]["end"] < times[second_start]["start"]:
          return 0
  
      return (
          (times[second_end]["end"] - times[first_start]["start"])
          - (times[second_start]["start"] - times[first_start]["start"])
          - (times[second_end]["end"] - times[first_end]["end"])
      )
  
  
  if __name__ == "__main__":
      ret = solve(inputs(1))
      print(ret)
  
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"}]