import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        String length = s.next();
        String targetNum = s.next();
        String stringValue = s.next();
        int a = Integer.parseInt(targetNum) - 1;
        char[] carVals = stringValue.toCharArray();
        carVals[a] =
                Character.toLowerCase(carVals[a]);
        System.out.println(String.valueOf(carVals));
    }
}

/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