import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  }
} import java.util.*; util.* java public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  } main {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt() N sc.nextInt() sc.nextInt sc K = sc.nextInt(); K sc.nextInt() sc.nextInt sc char S[] = sc.next().toCharArray(); S sc.next().toCharArray() sc.next().toCharArray sc.next() sc.next sc S[K - 1] += 32 S[K - 1] S K - 1 K 1 32 System.out.println(S) System.out.println System.out System System.out S String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  }
} Main
import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt(), K = sc.nextInt();
    char S[] = sc.next().toCharArray();
    S[K - 1] += 32;
    System.out.println(S);
  }
}