There are 2 red pens, 2 blue pens, 2 yellow pens, and 2 green pens. Let a child randomly grab 2 pens. How many times does the child need to grab at least two pens to ensure that the pens he grabs at least twice are exactly the same type. (After each grab, put it back and grab another)
有红笔、蓝笔、黄笔、绿笔各2支，让一位小朋友随便抓2支，这位小朋友至少抓多少次才能确保他至少有两次抓到的笔的种类完全相同．(每抓一次后又放回再抓另一次)
<gadget id="calculator">1 * 10</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>