output_description: Print `Yes` if you will turn on the air conditioner; print `No` otherwise.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      X
attempt: input()
  s = input()
  
  
  def find_cost(s):
      counter, i, j = 0, 0, len(s) - 1
      while i < j:
          while i < len(s) and s[i] != "W":
              i += 1
          while j >= 0 and s[j] != "R":
              j -= 1
          if i < j:
              s[i], s[j] = s[j], s[i]
              counter += 1
          i += 1
          j -= 1
      for i in range(0, len(s) - 2):
          if s[i] == "W" and s[i + 1] == "R":
              counter += 1
      print(counter)
  
  
  s = list(s)
  find_cost(s)
  
problem_description: Statement
  
  You will turn on the air conditioner if, and only if, the temperature of the
  room is 30 degrees Celsius or above.
  
  The current temperature of the room is X degrees Celsius. Will you turn on the
  air conditioner?
samples: [{"input": "25", "output": "No\n    \n\n* * *"}, {"input": "30", "output": "Yes"}]