Farmer Joe's Pig Farm lies on the border of Oddsville and Four Hills, and is thus subject to the laws of both towns. Four Hills requires all pig farms to have exactly four pig pens, no more, no less. Oddsville requires that all pig pens hold an odd number of pigs greater than zero.Farmer Joe has 21 pigs. How can he comply with both laws without moving his farm, changing his business, or gaining or losing pigs?
