挑最短的会，反而排得少

三场会 [(0,4),(3,5),(4,8)]，一边按时长最短挑，一边按结束最早挑。运行下面这段程序：

def sched(iv, key):
    end = -1
    n = 0
    for s, e in sorted(iv, key=key):
        if s >= end:
            n += 1
            end = e
    return n

print(str(sched([(0, 4), (3, 5), (4, 8)], lambda t: t[1] - t[0])) + "/" + str(sched([(0, 4), (3, 5), (4, 8)], lambda t: t[1])))