15puzzleThe fifteen puzzle has 15 pieces, which are numbered from 1 to 15 and which lay in a square frame. You cannot take away the pieces; you slide them by using a free square. At the beginning the 15 numbers are mixed (left). You must order the numbers by sliding (right). You don't need special advice to find a solution. Everybody, who has some patience, can arrange the pieces in the right order. To ge
