output_description: Print the string obtained by replacing every character in S that differs from
  the K-th character of S, with `*`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      S
      K
attempt: # 入力が10**5とかになったときに100ms程度早い
  import sys
  
  read = sys.stdin.readline
  
  
  def read_ints():
      return list(map(int, read().split()))
  
  
  def read_a_int():
      return int(read())
  
  
  def read_matrix(H):
      """
      H is number of rows
      """
      return [list(map(int, read().split())) for _ in range(H)]
  
  
  def read_map(H):
      """
      H is number of rows
      文字列で与えられた盤面を読み取る用
      """
      return [read() for _ in range(H)]
  
  
  def read_col(H, n_cols):
      """
      H is number of rows
      n_cols is number of cols
  
      A列、B列が与えられるようなとき
      """
      ret = [[] for _ in range(n_cols)]
      for _ in range(H):
          tmp = list(map(int, read().split()))
          for col in range(n_cols):
              ret[col].append(tmp[col])
  
      return ret
  
  
  N = read_a_int()
  S = input()
  K = read_a_int()
  
  target = S[K - 1]
  
  ans = []
  for i in range(N):
      if S[i] != target:
          ans.append("*")
      else:
          ans.append(target)
  
  print(*ans, sep="")
  
problem_description: Statement
  
  You are given a string S of length N consisting of lowercase English letters,
  and an integer K. Print the string obtained by replacing every character in S
  that differs from the K-th character of S, with `*`.
samples: [{"input": "5\n    error\n    2", "output": "*rr*r\n    \n\nThe second character of S is `r`. When we replace every character in `error`\nthat differs from `r` with `*`, we get the string `*rr*r`.\n\n* * *"}, {"input": "6\n    eleven\n    5", "output": "e*e*e*\n    \n\n* * *"}, {"input": "9\n    education\n    7", "output": "******i**"}]