Main.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.util.regex.Pattern;

public class Main {
 public static void main(String[] args) throws IOException {
 BufferedReader reader;
 if (args.length > 0) {
 reader = new BufferedReader(new InputStreamReader(System.in));
 } else {
 reader = new BufferedReader(new StringReader(
 """
 1101111
 """
 ));
 }

 for(;;) {
 String line = reader.readLine();
 if (null == line) {
 break;
 }
 String converted = toHex(line);
 System.out.println(converted);
 }
 }

 public static String toHex(String binary) {
 if (binary.length() % 4 != 0) {
 // append zeros
 }
 if (!Pattern.matches("[01]*", binary)) {
 return null;
 }
 

 return "1";
 }

 public static String toBinary(String hex) {

 return "01";
 }
}