
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      String[] nyu=sc.nextLine().split(" ");
   //  String nyu=sc.nextLine();

int A=Integer.parseInt(nyu[0]);
int B=Integer.parseInt(nyu[1]);

String ny[]=sc.nextLine().split("");

for(int i=0;i<ny.length;i++){
if(i==B-1){
System.out.print(ny[i].toLowerCase());
}else{
System.out.print(ny[i]);
}

}

	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz