output_description: Print the string S after lowercasing the K-th character in it.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
      S
attempt: S = input()
  if (int(S[:2]) == 0) and (int(S[2:4])) == 0:
      print("{}".format("NA"))
  elif (int(S[:2]) == 0) and (12 < int(S[2:4])):
      print("{}".format("NA"))
  elif 12 < (int(S[:2])) and (int(S[2:4]) == 0):
      print("{}".format("NA"))
  elif (12 < int(S[:2])) and (12 < int(S[2:4])):
      print("{}".format("NA"))
  elif (int(S[:2]) == 0) and (int(S[2:4]) < 13):
      print("{}".format("YYMM"))
  elif (int(S[:2]) < 13) and (int(S[2:4]) == 0):
      print("{}".format("MMYY"))
  elif 0 < (int(S[:2]) < 13) and (0 < int(S[2:4]) < 13):
      print("{}".format("AMBIGUOUS"))
  elif int(S[:2]) < 13:
      print("{}".format("MMYY"))
  else:
      print("{}".format("YYMM"))
  
problem_description: Statement
  
  You are given a string S of length N consisting of `A`, `B` and `C`, and an
  integer K which is between 1 and N (inclusive). Print the string S after
  lowercasing the K-th character in it.
samples: [{"input": "3 1\n    ABC", "output": "aBC\n    \n\n* * *"}, {"input": "4 3\n    CABA", "output": "CAbA"}]