A rectangle is formed by combining two squares with side lengths of 13 cm. Find the perimeter of the rectangle.
用边长是13厘米的两个正方形拼成一个长方形．求长方形的周长．
<gadget id="calculator">13 + 13 + 13</gadget>
<output>39</output>

<gadget id="calculator">39 * 2</gadget>
<output>78</output>

<result>78</result>