https://www.acmicpc.net/problem/1931
import sys
input = sys.stdin.readline
N = int(input())
time = [list(map(int, input().split())) for _ in range(N)]
time.sort(key=lambda x: (x[1], x[0]))
cnt = 1
end = time[0][1]
for i in range(1, N):
if time[i][0] >= end:
cnt += 1
end = time[i][1]
print(cnt)
```