source_code: 
  import java.util.*;
  
  
  public class A
  {
     public static void main(String[] args)
     {
        new A(new Scanner(System.in));
     }
  
     public A(Scanner in)
     {
        TreeSet<String> ts = new TreeSet<String>();
        ArrayList<String> sr = new ArrayList<String>();
  
        String s = in.next();
        for (int i=0; i<s.length(); i++)
        {
           for (int j=i+1; j<=s.length(); j++)
           {
              String ss = s.substring(i, j);
              if (ts.contains(ss))
              {
                 sr.add(ss);
              }
              ts.add(ss);
           }
        }
  
        int res = 0;
        for (String ss : sr)
        {
           if (ss.length() > res)
              res = ss.length();
        }
  
        System.out.printf("%d%n", res);
     }
  }
  