import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    } main {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) String line = sc.nextLine(); line sc.nextLine() sc.nextLine sc String[] line1 = line.split(" "); line1 line.split(" ") line.split line " " int a = Integer.parseInt(line1[0]); a Integer.parseInt(line1[0]) Integer.parseInt Integer line1[0] line1 0 int b = Integer.parseInt(line1[1]); b Integer.parseInt(line1[1]) Integer.parseInt Integer line1[1] line1 1 String line2 = sc.nextLine(); line2 sc.nextLine() sc.nextLine sc char[] line3 = line2.toCharArray(); line3 line2.toCharArray() line2.toCharArray line2 char c = line2.charAt(b - 1); c line2.charAt(b - 1) line2.charAt line2 b - 1 b 1 c += 32 c 32 line3[b - 1] = c line3[b - 1] line3 b - 1 b 1 c for(char c1 : line3) {
            System.out.print(c1);
        } char c1 line3 {
            System.out.print(c1);
        } {
            System.out.print(c1);
        } System.out.print(c1) System.out.print System.out System System.out c1 String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    }
} Main
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        int a = Integer.parseInt(line1[0]);
        int b = Integer.parseInt(line1[1]);
        String line2 = sc.nextLine();
        char[] line3 = line2.toCharArray();
        
        char c = line2.charAt(b - 1);
        c += 32;
        line3[b - 1] = c;
        for(char c1 : line3) {
            System.out.print(c1);
        }
    }
}