How many different currency values can be formed with one piece of 10 yuan, one piece of 5 yuan, one piece of 2 yuan, and one piece of 1 yuan?
用一张10元、一张5元、一张2元、一张1元，可组成多少种不同的币值？
<gadget id="calculator">4 + 10 + 1</gadget>
<output>15</output>

<result>15</result>