A piece of white paper with a length of 13 decimeters and a width of 5 decimeters is surrounded to form a cylindrical paper tube. What is the lateral area of the paper tube in square decimeters?
把一张长13分米，宽5分米的白纸，围成一个圆柱形纸筒，这个纸筒的侧积是多少平方分米．
<gadget id="calculator">13 * 5</gadget>
<output>65</output>

<result>65</result>