Decompose A and B into prime factors: A=2*3*3*7, B=2*3*7, then what is the greatest common factor of A and B?
把A、B分解质因数为：A=2*3*3*7，B=2*3*7，那么A、B的最大公因数是多少．
<gadget id="calculator">2 * 3 * 7</gadget>
<output>42</output>

<result>42</result>