source_code: 
  
  import java.util.Scanner;
  
  public class A_YoureGivenAString {
  
      //1:11
      
      public static void main(String[] args) {
          Scanner s = new Scanner(System.in);
          String str = s.nextLine();
          
          for (int l = str.length()-1; l >= 1; l--) {
              for (int i = 0; i < str.length()-l+1; i++) {
                  String subs = str.substring(i, i+l);
                  if(str.lastIndexOf(subs) != i){
                      System.out.println(l);
                      return;
                  }
              }
          }
          System.out.println(0);
      }
  
  }
  