Numerical Puzzle - The Rules

You must arrange the numbers in order, from 1 to 15. The first four numbers, from 1 to 4, must be ordered on the first row, the next 4 numbers on the second row and so on. On the last row, in the right, the empty square must be placed.

Valid moves consist in swapping a numbered square with the empty square. Those 2 squares that are swapped must be neighbors (the numbered square must be placed at the left, right, upper or bottom side of the empty square).

Good luck at solving the puzzle!