culator__select-math-sign" name="operation" data-math-operation>
                        <option value="+">+</option>
                        <option value="-">-</option>
                        <option value="/">/</option>
                        <option value="*">*</option>
                        <option value="**">**</option>
                    </select>
                    <input class="calculator__input" data-math-value="second" placeholder="Enter second value...">
                    <button class="