Envío 2203

Código

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main{

	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int k = sc.nextInt();
		sc.close();
		Map<Character, Integer> m = new HashMap<Character, Integer>();
		int current = 0;
		Character c;
		Integer in, max = 0;
		for (int i = 0; i < s.length(); i++) {
			c = s.charAt(i);
			in = m.get(c);
			if (in != null) {
				m.put(c, m.get(c) + 1);
			} else {
				m.put(c, 1);
			}
			while (m.size() > k) {
				c = s.charAt(current++);
				in = m.get(c);
				if (in != null) {
					m.put(c, in - 1);
					if (m.get(c) == 0) {
						m.remove(c);
					}
				}
			}
			max = Math.max(max, 1 + i - current);
		}
		System.out.println(max);
	}

}