N,K=map(int,input().split())
A=[[int(x) for x in input().split()] for _ in range(K)]
A=sorted(A, key=lambda x: x[1])
ans=0
p=0
for i in range(K):
    if A[i][0]>p:
        ans+=1
        p=A[i][1]
print(N-ans)