In the three textbooks of History, Thinking, and English, each person can take 2 textbooks at will, and at least how many students take 2 textbooks must be the same.
在历史，思品，英语三种教科书中每人任意拿2本，至少多少个学生拿的教科书中一定有2本相同．
<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<result>7</result>