source_code: import java.util.*;
  import java.io.*;
  import java.math.*;
  
  public class Main {
      public static Scanner scan = new Scanner(System.in);
      public static boolean bg = true;
  
      public static void main(String[] args) throws Exception {
          String k1 = scan.next();
          HashSet<String> met = new HashSet();
          String ans = "";
          for (int i=1;i<=k1.length()-1;i++){
              for (int j=0;j+i<=k1.length();j++){
                  String cur = k1.substring(j, j+i);
                  if (!met.contains(cur)){
                      met.add(cur);
                  }
                  else {
                      if (cur.length()>ans.length())ans=cur;
                  }
              }
          }
          System.out.println(ans.length());
          
      }
  }
  