source_code: //contest 23. You're Given A String
  import java.util.*;
  public class ProblemA
  {
  	public static void main(String[] args)
  	{
  		Scanner keyboard = new Scanner(System.in);
  		String input = keyboard.nextLine();
  		boolean con = false;
  		for( int i = input.length()-1; i > 0 ; i--)
  		{	
  			for ( int j = 0; j+i< input.length(); j++ )
  				for( int k = j+1; k+i <= input.length(); k++ )
  					if( input.substring(j,j+i).equals( input.substring(k,k+i) ) ) 
  					{
  						System.out.print(i+"\n");
  						k = input.length()+1;
  						j = input.length();
  						i = -1;
  						con = true;
  					}
  		}
  		if( con == false )
  			System.out.print(0+"\n");
  	}	
  }