output_description: Print the string representing the type of the contest held this week.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
attempt: n = list(str(input()))
  if n[1] == "B":
      n[1] = "R"
  elif n[1] == "R":
      n[1] == "B"
  print("".join(n))
  
problem_description: Statement
  
  AtCoder Inc. holds a contest every Saturday.
  
  There are two types of contests called ABC and ARC, and just one of them is
  held at a time.
  
  The company holds these two types of contests alternately: an ARC follows an
  ABC and vice versa.
  
  Given a string S representing the type of the contest held last week, print
  the string representing the type of the contest held this week.
samples: [{"input": "ABC", "output": "ARC\n    \n\nThey held an ABC last week, so they will hold an ARC this week."}]