Use a 50 cm long lace to surround a square photo frame with a side length of 10 cm. How many centimeters are left in the lace?
用一根长50厘米的花边将边长10厘米的正方形相框围一圈，花边还剩下多少厘米？
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<result>10</result>