import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    }
} Main public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    } main {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) sc.next() sc.next sc int k = Integer.parseInt(sc.next()); k Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc String s = sc.next(); s sc.next() sc.next sc char[] c = s.toCharArray(); c s.toCharArray() s.toCharArray s if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        } c[k-1] == 'A' c[k-1] c k-1 k 1 'A' {
            c[k-1] = 'a';
        } c[k-1] = 'a' c[k-1] c k-1 k 1 'a' if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        } c[k-1] == 'B' c[k-1] c k-1 k 1 'B' {
            c[k-1] = 'b';
        } c[k-1] = 'b' c[k-1] c k-1 k 1 'b' {
            c[k-1] = 'c';
        } c[k-1] = 'c' c[k-1] c k-1 k 1 'c' System.out.println(c) System.out.println System.out System System.out c String[] args args public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    }
} public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        
        sc.next();
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        
        char[] c = s.toCharArray();
        if(c[k-1] == 'A'){
            c[k-1] = 'a';
        }else if(c[k-1] == 'B'){
            c[k-1] = 'b';
        }else{
            c[k-1] = 'c';
        }
        
        System.out.println(c);
    }
}