if (diff < 0) insert(index, arg, left[slot], slot, replace, true);
else insert(index - sizeof(left[slot]) - 1, arg, right[slot], slot, replace, false);
balance(slot, p);
if (diff < 0) insert(index, arg, left[slot], slot, replace, true);
else insert(index - sizeof(left[slot]) - 1, arg, right[slot], slot, replace, false);
balance(slot, p);