source_code: import java.util.*;
  
  public class test 
  {    
      static boolean isOK(String str, int len)
      {
  	HashSet<String> hs=new HashSet<String>();
  	
  	for(int i=0;i<=str.length()-len;i++)
  	{
  	    String s=str.substring(i,len+i);
  	    if(hs.contains(s))
  		return true;
  	    else
  		hs.add(s);
  	}
  	
  	return false;
      }
      public static void main(String[] args) 
      {
          Scanner in=new Scanner(System.in);
          String str=in.next();
          
          int i;
          for(i=str.length()-1;i>=1;i--)
              if(isOK(str,i))
              {
          	break;
              }
          
          System.out.println(i);
      }
  }
  
  