18. A wire 144 cm long is to be formed into a rectangle with both length and width being integers in centimeters. There are $\qquad$ different ways to do this.
Because the perimeter of the rectangle is 144 cm, the sum of the length and width is $144 \div 2=72$ (cm). Since the length and width of the rectangle are both integers in centimeters, $72=71+1=70+2=69+3=68+4 \cdots \cdots=37+35=36+36$, there are a total of $71-36+1=36$ (ways).