N,M=map(int,input().split())
query=[]
for m in range(M):
    L,R=map(int,input().split())
    query.append((R,L))
query.sort()
queue=[]
for R,L in query:
    if not queue or queue[-1]<L:
        queue.append(R)
ans=N-len(queue)
print(ans)