n, m = map(int, input().split())
r = []
for i in range(m):
    r.append(list(map(int,input().split())))

r.sort()
r.sort(key = lambda x : x[1])

cnt = 0
z = -1
for x in r:
    if z < x[0]:
        cnt += 1
        z = x[1]
print(n - cnt)