docs: public static int[] insertArray(int[] original, int index, int[] inserted) {
          int[] modified = new int[original.length + inserted.length];
          System.arraycopy(original, 0, modified, 0, index);
          System.arraycopy(inserted, 0, modified, index, inserted.length);
          System.arraycopy(original, index, modified, index + inserted.length, modified.length - index - inserted.length);
          return modified;
      }