There are 10 stamps of 2 yuan, 3 yuan, and 4 yuan in the wallet. Now I want to send a letter with 12 yuan postage. Without looking at it, I take out several stamps from the wallet. If you can make up a stamp combination of 12 yuan, then at least how many stamps must be drawn.
皮夹里有2元、3元、4元的邮票各10张，现在要寄一封12元邮资的信，不用眼睛看，从皮夹中抽出若干张邮票，为了保证从抽出的邮票中一定能凑出12元的邮票组合来，那么至少要抽出多少张邮票．
<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<result>7</result>