n,m = map(int,input().split())
lr = []
for _ in range(m):
    lr.append(list(map(int,input().split())))
lr.sort(key = lambda x:(x[1],x[0]))
ans = n
R = 0
for i in range(m):
    l,r = lr[i]
    if l > R:
        ans -= 1
        R = r
print(ans)