Tic-tac-toe P54928

In the tic-tac-toe game, two players compete to be the first to place in a board 3 × 3 three pieces forming a vertical, horizontal or diagonal line. A player places white pieces, the other one uses black pieces always taking turns. Starts the player with the white pieces. The game ends when one of the payers reach to place three pieces forming a line, or when the nine positions are taken.

Your task is to write a program that indicates if a given configurations of a tic-tac-toe game is correct or not. That is, it must indicate if the configuration could be obtained in a game playing according to the rules.

Input

The input consists of three line with three chacteres each one. A ’W’ indicates a white piece. A ’B’ indicates a black piece. A dot indicates an empty position.

Output

Your program must print "possible" or "impossible" as required.