be1ay

def fl(l):
    if len(l) > 2:
        return '%s-%s' % (l[0], l[-1])
    elif len(l) == 2:
        return '%s, %s' % (l[0], l[-1])
    else:
        return '%s' % l[0]

def cc(l):
    r = []
    b = []
    for i in l:
        if len(b) > 0:
            if i - b[-1] == 1:
                b.append(i)
            else:
                r.append(fl(b))
                b = [i]
        else:
            b.append(i)
    else:
        r.append(fl(b))

    return ', '.join(r)