Use pieces of paper 25 cm long and 15 cm wide to form a square. What is the minimum number of such pieces of paper needed?
用长25厘米、宽15厘米的纸片拼成一个正方形，最少需要多少张这样的纸片．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>