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: N = int(input())
  y = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  one = [1]
  zero = [0]
  p = [1, 2, 3, 4, 5, 6, 7, 8, 9]
  q = [0, 1, 2]
  a = N // 1000
  b = (N - (a * 1000)) // 100
  c = (N - (a * 1000) - (b * 100)) // 10
  d = N - (a * 1000) - (b * 100) - (c * 10)
  
  if ((a in one) and (b in q) or (a in zero) and (b in p)) and (
      (c in one) and (d in q) or (c in zero) and (d in p)
  ):
      print("AMBIGUOUS")
  elif (a in y) and (b in y) and ((c in one) and (d in q) or (c in zero) and (d in p)):
      print("YYMM")
  elif ((a in one) and (b in q)) or ((a in zero) and (b in p)) and (c in y) and (d in y):
      print("MMYY")
  else:
      print("NA")
  
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"}]