source_code: import java.util.*;
  import java.io.*;
  
  public class a {
  	public static void main(String[] args) {
  		Scanner sc = new Scanner(System.in);
  		String s = sc.next();
  		
  		int len = s.length();
  		for(int i=len-1; i>=1; --i) {
  			for(int j=0; j<=len - i; ++j) {
  				String ss = s.substring(j, j+i);
  
  				if(s.substring(j+1).indexOf(ss)!=-1) {
  					System.out.println(ss.length());
  					return;
  				} 
  			}
  		}
  		System.out.println(0);
  	}
  }
  