N, M = map(int, input().split())
data = []
for i in range(M):
    l,r = map(int, input().split())
    data.append([l, r])

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

cnt = 1
pre = data[0][1]+1
for i in range(1, M):
    if pre < data[i][0]:
        cnt += 1
        pre = data[i][1]+1

print(N-cnt)