Who won the game?

Question

Task

Everyone knows the game "Tic-Tac-Toe". Your task is it, to evaluate an ascii tic-tac-toe matchfield. Your Programm/Function should output/return the winner: O, X or nobody (N).

Pattern

X|O|X
O|X|O
O|O|X

In this case your programm/function should output/return 'X'

Rules

• Input can come from STDIN, function arguments, command line argument, file, whatever suits you.

• The program can be a function, full program, whatever works, really, as long as no external files are needed to run it.

• You can assume that the input is valid.

Test Cases

X|O|X
O|X|X  = O
O|O|O

O|X|O
X|X|O  = X
O|X|X

X|O|X
O|X|O  = N
O|X|O

This is code-colf, so the shortest answer (in bytes) wins.