source_code: import java.util.Scanner;
  
  
  public class GiveString23A {
      public static void main(String[] args)
      {
          Scanner in = new Scanner(System.in);
          String stroke = in.next();
          char[] s = new char [stroke.length()];
          for (int i=0;i<stroke.length();i++)
              s[i]=stroke.charAt(i);
          int dlina = 0;
          for (int i=0;i<s.length-1;i++)
              for (int j=i+1;j<s.length;j++)
                  for (int k=0;k<(s.length-j);k++)
                      if (s[i]==s[j])
                      {
                          int ik=i+k;
                          int jk = j+k;
                          if (s[ik]==s[jk])
                          {
                              if (dlina<k+1)
                                  dlina=k+1;      
                          }
                          else 
                          break;
                      }       
          System.out.println(dlina);
      }
  }
  