def cut_up_url(url):
    """ 
    Input:  A URL string consistent w/ runbritain.com. Here is an ex)
    https://www.runbritainrankings.com/results/results.aspx?meetingid=201320&pagenum=1
    
    Output: Unique ID int for a particular race, which is how
    I cross-reference GPS info with race info
    """ 
    flag = 'meetingid='
    start = url.find(flag) + len(flag) 
    end   = url.find('&')
    substr = url[start:end]
    return int(substr)