source_code: import java.io.*;
  public class A23 {
      public static void main(String[] args) throws IOException   {
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          String s = br.readLine();
          for(int length = s.length(); length > 0; length--)      {
              for(int start = 0; start + length <= s.length(); start++)       {
                  String test = s.substring(start, start+length);
                  if(s.indexOf(test) != s.lastIndexOf(test))  {
                      System.out.println(length);
                      return;
                  }
              }
          }
          System.out.println(0);
      }
  }
  