text: def mutate_string(string, position, character):
      
       string = string[:position] + character + string[position +1:] 
       return string
  
  if __name__ == '__main__':
      s = raw_input()
      i, c = raw_input().split()
      s_new = mutate_string(s, int(i), c)
      print s_new
  