백준 1931_회의실배정 [python/파이썬] + sorted by key

import sys
 
num = int(input())
meeting_list = []
for case in range(num):
    meeting_list.append(list(map(int, sys.stdin.readline().strip().split())))
 
# 회의가 끝나는 시간이 빠른 순으로 재정렬
meeting_list = sorted(meeting_list, key=lambda x: (x[1],x[0]))
 
post_meeting = [0, 0]
count = 0
for meeting in meeting_list:
    if post_meeting[1] > meeting[0]:
        pass
    else:
        count += 1
        post_meeting = [meeting[0], meeting[1]]
 
print(count)