public static int toys(List<Integer> w) {
      Collections.sort(w);
      int n = w.size();
      int containerCount = 1;
      int minUnit = w.get(0);
      for(int i = 1; i < n; i++ ) {
        if(w.get(i) > minUnit + 4) {
          minUnit = w.get(i);
          containerCount++;
        }
      }
     return containerCount;
    }

}