Zhang Dong participated in a party attended by 18 people. He shook hands with each of these people. How many times did Zhang Dong shake hands in total?
张东参加由18个人出席的联欢会，他与这些人一一握手，张东一共握了几次手？
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<result>17</result>