A rectangular iron sheet, 13 cm long and 7 cm wide, cut out a largest square from it, what is the area of the remaining part in square centimeters?
一块长方形铁皮，长13厘米，宽7厘米，从它上面剪下一个最大的正方形，剩余部分的面积是多少平方厘米．
<gadget id="calculator">13 * 7</gadget>
<output>91</output>

<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<gadget id="calculator">91 - 49</gadget>
<output>42</output>

<result>42</result>