Five children are having a snowball fight together. If each child throws a snowball to every other child, how many snowballs are thrown in total?
5个小朋友在一起打雪仗，如果每人都向其他每个小朋友掷一个雪球，那么一共掷出多少个雪球．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>