N, M = map(int, input().split())
LR = []
for _ in range(M):
	L, R = map(int, input().split())
	LR.append((R, L))
LR.sort()
ans = 0
nr = 0
for r, l in LR:
	if l > nr:
		nr = r
		ans += 1
print(N - ans)