import sys
if sys.platform =='ios':
	import clipboard
	a=clipboard.get()
	a = a.split('\n')
	text = '\n'.join(a)
	with open('input_file.txt','w') as f:
		f.write(text)
	sys.stdin = open('input_file.txt')
	
from sys import stdin

readline = stdin.readline

N, M = map(int, readline().split())
LR = [list(map(int, readline().split())) for _ in range(M)]

result = N
t = -1
for L, R in sorted(LR, key=lambda x: x[1]):
    if L <= t <= R:
        continue
    result -= 1
    t = R
print(result)