/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	//abcabcdbd 
	//Sliding window solution Time: O(n), Space: O(1)
	
	public static void main (String[] args) throws java.lang.Exception
	{
		System.out.println(getLongestStringWithoutRepetitions("abcabcdbd"));
		System.out.println(getLongestStringWithoutRepetitions(""));
		System.out.println(getLongestStringWithoutRepetitions("aaabbb"));
		System.out.println(getLongestStringWithoutRepetitions("aaa"));
		System.out.println(getLongestStringWithoutRepetitions("abc"));
		System.out.println(getLongestStringWithoutRepetitions("abbcdecb"));
	}
	
	private static int getLongestStringWithoutRepetitions(String input) {
		int start=0, end=0, result=0;
		int[] count = new int[26];
		while(end<input.length()) {
			count[(int)(input.charAt(end)-'a')]++;
			if(count[(int)(input.charAt(end)-'a')]>1) {
				while(start<=end) {
					start++;
					count[(int)(input.charAt(start-1)-'a')]--;
					
					if(count[(int)(input.charAt(start-1)-'a')]==1) {
						break;
					}
				}
			}
			result = Math.max(result, end-start+1);
			end++;
		}
		return result;
	}
}