n, m = map(int, input().split())
lr = [list(map(int, input().split())) for i in range(m)]
lr.sort(key=lambda x:x[1])
last = lr[0][1]
cnt = 1
for i in range(1, m):
    l, r = lr[i]
    if last < l:
        cnt += 1
        last = r
print(n - cnt)