import java.util.*;

import java.util.LinkedList;

/**

* Created by dheeraj on 12/20/14.

*/

public class EmptyRoom {

private List<Character> roomList = new LinkedList<Character>();

private List<Character> nonroomList = new LinkedList<Character>();

String string;

int numRooms;

public EmptyRoom(String string, int numRooms) {

this.string = string;

this.numRooms = numRooms;

}

private void findAnswer() {

char data;

for (int x = 0; x < string.length(); x++) {

data = string.charAt(x);

if(roomList.contains(data)){

roomList.remove(roomList.indexOf(data));

}else if(roomList.size() < numRooms){

roomList.add(data);

}else if(nonroomList.contains(data)){

//do nothig

}else{

nonroomList.add(data);

}

}

System.out.println(nonroomList.size());

}

public static void main(String[] args){

EmptyRoom emptyRoom = new EmptyRoom("ABCBCA",1);

emptyRoom.findAnswer();

}

}