The prizes at the school's New Year's Day party are fountain pens, ballpoint pens, pencils and fountain pens. Each winning student can choose two different pens. At least how many students have won the prize, in order to ensure that 4 of them will get the same prize.
学校庆祝元旦联欢会上的奖品是钢笔、圆珠笔、铅笔和水笔，每位获奖学生可任选两只不同的笔．至少多少位同学获奖，才能保证其中必有4人拿到的奖品完全相同．
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">18 + 1</gadget>
<output>19</output>

<result>19</result>