There is a piece of 10 yuan, a piece of 5 yuan, and a piece of 2 yuan, how many different currency values can be formed.
有一张10元、一张5元、一张2元，共可以组成多少种不同的币值．
<gadget id="calculator">3 + 3 + 1</gadget>
<output>7</output>

<result>7</result>