source_code: import java.util.*;
  public class P023A {
      public static void main(String[] args)
      {
          Scanner in = new Scanner(System.in);
          String line = in.next();
          
          HashSet<String> hash = new HashSet<String>();
          
          int ans = 0;
          for (int len = line.length()-1; len > 0; --len)
          {
              for (int i = 0; i + len <= line.length(); ++i)
              {
                  String sub = line.substring(i, i+len);
                  if (hash.contains(sub))
                  {
                      ans = Math.max(ans, sub.length());
                  }
                  
                  hash.add(sub);
              }
          }
          
          System.out.println(ans);
      }
  }
  