def compare_version_numbers(version1, version2):
    """
    Compare two version numbers.

    Return -1 if version1 < version2, 0 if version1 == version2, +1 if version1 > version2
    Version :== (k,l,m,n)
    k, l, m, n := int
    """
    if version1 is None:
        if version2 is None:
            return 0
        else:
            return -1
    elif version2 is None:
        return +1
    else:
        for i in range(0, 4):
            if version1[i] > version2[i]:
                return +1
            elif version1[i] < version2[i]:
                return -1
        return 0