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: import sys
  from io import StringIO
  import unittest
  
  
  def resolve():
      N, K = map(int, input().split())
      S = list(input())
      S[K - 1] = S[K - 1].lower()
      print("".join(S))
  
  
  class TestClass(unittest.TestCase):
      def assertIO(self, input, output):
          stdout, stdin = sys.stdout, sys.stdin
          sys.stdout, sys.stdin = StringIO(), StringIO(input)
          resolve()
          sys.stdout.seek(0)
          out = sys.stdout.read()[:-1]
          sys.stdout, sys.stdin = stdout, stdin
          self.assertEqual(out, output)
  
      def test_入力例_1(self):
          input = """3 1
  ABC"""
          output = """aBC"""
          self.assertIO(input, output)
  
      def test_入力例_2(self):
          input = """4 3
  CABA"""
          output = """CAbA"""
          self.assertIO(input, output)
  
  
  if __name__ == "__main__":
      resolve()
  
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"}]