source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  public class A implements Runnable {
      private void solve() throws IOException {
          String str = nextToken();
          for (int i=str.length()-1; i>=0; --i)
              for (int j=0; j+i<=str.length(); ++j)
                  if (str.substring(j+1).contains(str.substring(j, j+i))) {
                      writer.println(i);
                      return;
                  }
          writer.println(0);
      }
  
      public static void main(String[] args) {
          new Thread(new A()).start();
      }
  
      BufferedReader reader;
      StringTokenizer tokenizer;
      PrintWriter writer;
  
      public void run() {
          try {
              reader = new BufferedReader(new InputStreamReader(System.in));
              tokenizer = null;
              writer = new PrintWriter(System.out);
              solve();
              reader.close();
              writer.close();
          } catch (Exception e) {
              e.printStackTrace();
              System.exit(1);
          }
      }
  
      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 nextToken() throws IOException {
          while (tokenizer == null || !tokenizer.hasMoreTokens()) {
              tokenizer = new StringTokenizer(reader.readLine());
          }
          return tokenizer.nextToken();
      }
  }