백준 16472

package baekjoon.투포인터;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

class Main16472 {

   static int N;
   static String S;
   static int[] cnt;

   public static void main(String[] args) throws Exception {
      input();
      go();
   }

   private static void add(char x) {
      cnt[x - 'a']++;
   }

   private static void remove(char x) {
      cnt[x - 'a']--;
   }

   private static void go() {
      int len = S.length(), ans = 0;
      for (int R = 0, L = 0; R < len; R++) {
         add(S.charAt(R));
         int kind;
         while (true) {
            kind = 0;
            for (int i = 0; i < 26; i++) {
               if (cnt[i] != 0)
                  kind++;
            }
            if (kind <= N) {
               break;
            }
            remove(S.charAt(L));
            L++;
         }
         ans = Math.max(ans, R - L + 1);
      }
      System.out.println(ans);
   }

   private static void input() throws IOException {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      N = Integer.parseInt(br.readLine());
      S = br.readLine();
      cnt = new int[26];
   }
}