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