import java.util.Scanner;
 
class Main {
  static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
      
      int a = sc.nextInt();
      int b = sc.nextInt();
      String s = sc.next();
      char[] s_chars = s.toCharArray();
      s_chars[b-1]+=32;
      
      System.out.print(s_chars);
      

      
    }
} import java.util.Scanner; Scanner java.util class Main {
  static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
      
      int a = sc.nextInt();
      int b = sc.nextInt();
      String s = sc.next();
      char[] s_chars = s.toCharArray();
      s_chars[b-1]+=32;
      
      System.out.print(s_chars);
      

      
    }
} Main static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) public static void main(String[] args) {
      
      int a = sc.nextInt();
      int b = sc.nextInt();
      String s = sc.next();
      char[] s_chars = s.toCharArray();
      s_chars[b-1]+=32;
      
      System.out.print(s_chars);
      

      
    } main {
      
      int a = sc.nextInt();
      int b = sc.nextInt();
      String s = sc.next();
      char[] s_chars = s.toCharArray();
      s_chars[b-1]+=32;
      
      System.out.print(s_chars);
      

      
    } int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc String s = sc.next(); s sc.next() sc.next sc char[] s_chars = s.toCharArray(); s_chars s.toCharArray() s.toCharArray s s_chars[b-1]+=32 s_chars[b-1] s_chars b-1 b 1 32 System.out.print(s_chars) System.out.print System.out System System.out s_chars String[] args args
import java.util.Scanner;
 
class Main {
  static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) {
      
      int a = sc.nextInt();
      int b = sc.nextInt();
      String s = sc.next();
      char[] s_chars = s.toCharArray();
      s_chars[b-1]+=32;
      
      System.out.print(s_chars);
      

      
    }
}