output_description: Print the earliest possible time for the kangaroo to reach coordinate X.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      X
attempt: import fileinput
  
  
  def algorithm(X):
      return int(X // 2) if X > 2 else X
  
  
  def pass_inputs(input_lines):
      X = input_lines[0][0]
      return algorithm(X)
  
  
  def convert_int(s):
      try:
          r = int(s)
      except ValueError:
          r = s
      return r
  
  
  def run():
      out = pass_inputs(
          [[convert_int(v) for v in l.strip().split(" ")] for l in fileinput.input()]
      )
      print(out)
  
  
  if __name__ == "__main__":
      run()
  
problem_description: Statement
  
  There is a kangaroo at coordinate 0 on an infinite number line that runs from
  left to right, at time 0. During the period between time i-1 and time i, the
  kangaroo can either stay at his position, or perform a jump of length exactly
  i to the left or to the right. That is, if his coordinate at time i-1 is x, he
  can be at coordinate x-i, x or x+i at time i. The kangaroo's nest is at
  coordinate X, and he wants to travel to coordinate X as fast as possible. Find
  the earliest possible time to reach coordinate X.
samples: [{"input": "6", "output": "3\n    \n\nThe kangaroo can reach his nest at time 3 by jumping to the right three times,\nwhich is the earliest possible time.\n\n* * *"}, {"input": "2", "output": "2\n    \n\nHe can reach his nest at time 2 by staying at his position during the first\nsecond, and jumping to the right at the next second.\n\n* * *"}, {"input": "11", "output": "5"}]