docs: public void put(int key, int value) {
          if (key < 0) Kit.codeBug();
          int index = ensureIndex(key, true);
          if (ivaluesShift == 0) {
              int N = 1 << power;
              // keys.length can be N * 2 after clear which set ivaluesShift to 0
              if (keys.length != N * 2) {
                  int[] tmp = new int[N * 2];
                  System.arraycopy(keys, 0, tmp, 0, N);
                  keys = tmp;
              }
              ivaluesShift = N;
          }
          keys[ivaluesShift + index] = value;
      }