N,M = map(int, input().split())
L = [[0] * 2 for i in range(M)]
for i in range(M):
    L[i][0],L[i][1]=map(int, input().split())
L = sorted(L, key=lambda x: x[1])  #[1]に注目してソート
ans = N
temp = -1
for lr in L:
    l=lr[0]
    r=lr[1]
    if temp<l:
        temp=r
        ans-=1
print(ans)