import re

def up(num, dif):
    vals = []
    for i in xrange(dif):
        num += 1
        vals.append(num)
    return vals

def down(num, dif):
    vals = []
    if num > 1:
        count = 0
        while num > 1 and count < dif:
            num -= 1
            vals.append(num)
            count += 1
        return vals
    else:
        return [num]

def expand(trackbacks, dif):
    new_urls = []
    for trackback in trackbacks:
        m = re.match('(http[^"s]+/)([0-9]+)[/]?$', trackback)
        if m:
            url = m.group(1)
            post_id = int(m.group(2))
            ids = []
            ids.extend(up(post_id, dif))
            ids.extend(down(post_id, dif))
            new_urls.extend([url + str(id) for id in ids])
    return new_urls