N,M = map(int,input().split())

dat = [0] * M
for _ in range(M):
    l,r = map(int,input().split())
    dat[_] = (r,l)
dat.sort(reverse = True)
count = 0
now = 0
while len(dat):
    r,l = dat.pop()
    if l > now:
        count += 1
        now = r
print(N - count)