Xiao Gang originally had some pictures. His friend gave him 5 pictures, and he gave his younger brother 4 pictures. Later, he bought another 24 pictures. At this time, there were 33 pictures in total. How many pictures did Xiao Gang originally have?
小刚原来有一些画片，朋友送给他5张，他又送给弟弟4张，后来又买了24张，这时共有33张，小刚原来有多少张画片？
<gadget id="calculator">33 - 24</gadget>
<output>9</output>

<gadget id="calculator">4 - 5</gadget>
<output>-1</output>

<gadget id="calculator">9 + (-1)</gadget>
<output>8</output>

<result>8</result>