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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def choose_num(x, y):
    """This function takes two positive numbers x and y and returns the biggest even integer number that is in the range [x, y] inclusive. If there's no such number, then the function should return -1. choose_num(12, 15) = 14 choose_num(13, 12) = -1 """
    if x > y:
        return -1
    if y % 2 == 0:
        return y
    if x == y:
        return -1
    return y - 1
