import java.util.*;

public class Main {
	public static void main(String[] args) {  
  		Scanner sc = new Scanner(System.in);
		int length = sc.nextInt();
      	int lowPos = sc.nextInt();
      	String str = sc.next();
      
      	String[] ary = str.split("", 0);
      	for(int i = 0; i < length; i++) {
        	if(i == lowPos -1 ) ary[i] = ary[i].toLowerCase();
          	System.out.print(ary[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