from collections import defaultdict

N,M=map(int,input().split())


I=[]
for _ in range(M):
    l,r=map(int,input().split())
    I.append((l,r))

I.sort(key=lambda x:x[1])
R=-1
X=0

for l,r in I:
    if R<l:
        X+=1
        R=r

print(N-X)