code: import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  public class ABC {
  
      public static void main(String[] args) {
          List<String> blocks = Arrays.asList(
                  "BO", "XK", "DQ", "CP", "NA",
                  "GT", "RE", "TG", "QD", "FS",
                  "JW", "HU", "VI", "AN", "OB",
                  "ER", "FS", "LY", "PC", "ZM");
  
          for (String word : Arrays.asList("", "A", "BARK", "BOOK", "TREAT", "COMMON", "SQUAD", "CONFUSE")) {
              System.out.printf("%s: %s%n", word.isEmpty() ? "\"\"" : word, canMakeWord(word, blocks));
          }
      }
  
      public static boolean canMakeWord(String word, List<String> blocks) {
          if (word.isEmpty())
              return true;
  
          char c = word.charAt(0);
          for (int i = 0; i < blocks.size(); i++) {
              String b = blocks.get(i);
              if (b.charAt(0) != c && b.charAt(1) != c)
                  continue;
              Collections.swap(blocks, 0, i);
              if (canMakeWord(word.substring(1), blocks.subList(1, blocks.size())))
                  return true;
              Collections.swap(blocks, 0, i);
          }
  
          return false;
      }
  }
  