 data-key="5">5</button>
                <button class="number" data-key="6">6</button>
                <button class="pink function" id="subtract">-</button>
            </div>
            <div class="row">
                <button class="number" data-key="1">1</button>
                <button class="number" data-key="2">2</button>
                <button class="number" data-key="3">3</button>
                <button class="pink function" id="add">+</button>
            </div>
            <div class="row">
