Four fours is a mathematical puzzle. It is often use with older children to explore numbers and mathematical expressions, but many adults have also found it enjoyable. The goal of four fours is to find the simplest mathematical expression for every whole number from 0 to some maximum, using only common mathematical symbols and the digit four (no other digit is allowed). Most versions of four fours require that each expression have exactly four fours, but some variations require that each expression have the minimum number of fours.