source_code: import java.io.*;
  import java.util.*;
  
  import static java.lang.Math.*;
  import static java.util.Arrays.fill;
  import static java.util.Arrays.binarySearch;
  import static java.util.Arrays.sort;
  
  public class Main {
  	public static void main(String[] args) throws IOException {
  		try {
  			if (new File("input.txt").exists())
  				System.setIn(new FileInputStream("input.txt"));
  		} catch (SecurityException e) {}
  		
  		new Main().run();
  	}
  
  	BufferedReader in;
  	PrintWriter out;
  	StringTokenizer st = new StringTokenizer("");
  	
  	void run() throws IOException {
  		in = new BufferedReader(new InputStreamReader(System.in));
  		out = new PrintWriter(System.out);
  
  		String s = in.readLine();
  		
  		for (int len = s.length() - 1; len > 0; len--) {
  			Set<String> set = new HashSet<String>();
  			for (int i = 0; i + len <= s.length(); i++) {
  				String ss = s.substring(i, i + len);
  				if (set.contains(ss)) {
  					out.println(len);
  					out.close();
  					return;
  				}
  				set.add(ss);
  			}
  		}
  		out.println(0);
  		out.close();
  	}
  	
  	String nextToken() throws IOException {
  		while (!st.hasMoreTokens())
  			st = new StringTokenizer(in.readLine());
  		return st.nextToken();
  	}
  	
  	int nextInt() throws IOException {
  		return Integer.parseInt(nextToken());
  	}
  	
  	long nextLong() throws IOException {
  		return Long.parseLong(nextToken());
  	}
  	
  	double nextDouble() throws IOException {
  		return Double.parseDouble(nextToken());
  	}
  	
  	String nextLine() throws IOException {
  		st = new StringTokenizer("");
  		return in.readLine();
  	}
  	
  	boolean EOF() throws IOException {
  		while (!st.hasMoreTokens()) {
  			String s = in.readLine();
  			if (s == null)
  				return true;
  			st = new StringTokenizer(s);
  		}
  		return false;
  	}
  }
  