import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    } main {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int k = Integer.parseInt(sc.next()); k Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc String s = sc.next(); s sc.next() sc.next sc for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        } {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        } if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            } i == k - 1 i k - 1 k 1 {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } System.out.print(Character.toLowerCase(s.charAt(i))) System.out.print System.out System System.out Character.toLowerCase(s.charAt(i)) Character.toLowerCase Character s.charAt(i) s.charAt s i {
                System.out.print(s.charAt(i));
            } System.out.print(s.charAt(i)) System.out.print System.out System System.out s.charAt(i) s.charAt s i System.out.println() System.out.println System.out System System.out String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int k = Integer.parseInt(sc.next());
        String s = sc.next();
        for (int i = 0; i < n; i++) {
            if (i == k - 1) {
                System.out.print(Character.toLowerCase(s.charAt(i)));
            } else {
                System.out.print(s.charAt(i));
            }
        }
        System.out.println();
    }
}