import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        String s = sc.next();
        int p = -1;
        ArrayList<Integer> list = new ArrayList();
        for (int i = 0; i < n; i++) {
            if (s.charAt(i) == 'O') {
                p = 0;
            } else if (s.charAt(i) == 'K' && p != -1) {
                p++;
            } else if (s.charAt(i) == 'U' && p != -1) {
                list.add(p);
                p = -1;
            }
        }
        list.sort(Integer::compareTo);
        int j = 0;
        if (!list.isEmpty()) {
            for (j = 0; j < list.size(); j++) {
                m -= list.get(j);
                if (m < 0) {
                    break;
                }
            }
        }
        System.out.println(j);
    }
}