from operator import itemgetter

N,M=map(int,input().split())
LR=[tuple(map(int,input().split())) for i in range(M)]

LR.sort(key=itemgetter(0))
LR.sort(key=itemgetter(1))

leftmost=-1
ANS=0
for x,y in LR:
    if x>leftmost:
        leftmost=y
        ANS+=1
print(N-ANS)