Little Ding Ding is going to nail 10 photos in a row on the wall. Both sides of each photo must be nailed, and the same nail can nail two adjacent photos. How many nails are needed to finish nailing these photos?
小丁丁准备把10张照片在墙上钉成一排．每一张照片的两边都要用钉子钉住，同一个钉子可以钉住相邻的两张照片．钉完这些照片，一共需要多少个钉子．
<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>