import java.io.*;
public class Main
{
    public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
}
} import java.io.*; io.* java public class Main
{
    public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
}
} Main public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
} main {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
} BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) String line = br.readLine(); line br.readLine() br.readLine br String []tokens = line.split(" "); tokens line.split(" ") line.split line " " int n = Integer.parseInt(tokens[0]); n Integer.parseInt(tokens[0]) Integer.parseInt Integer tokens[0] tokens 0 int K = Integer.parseInt(tokens[1]); K Integer.parseInt(tokens[1]) Integer.parseInt Integer tokens[1] tokens 1 String S=br.readLine(); S br.readLine() br.readLine br int p=S.charAt(K-1); p S.charAt(K-1) S.charAt S K-1 K 1 char x=(char)(p+32); x (char)(p+32) p 32 System.out.print(S.substring(0,(K-1))+x+S.substring(K)) System.out.print System.out System System.out S.substring(0,(K-1))+x+S.substring(K) S.substring(0,(K-1))+x+S.substring(K) S.substring(0,(K-1)) S.substring S 0 (K-1) K 1 x S.substring(K) S.substring S K String []args args public class Main
{
    public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
}
} public class Main
{
    public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
}
} Main
import java.io.*;
public class Main
{
    public static void main(String []args)throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String []tokens = line.split(" ");
        int n = Integer.parseInt(tokens[0]);
        int K = Integer.parseInt(tokens[1]);
        String S=br.readLine();
        int p=S.charAt(K-1);
        char x=(char)(p+32);
System.out.print(S.substring(0,(K-1))+x+S.substring(K));
}
}
