n,m = map(int,input().split())
LR = [list(map(int,input().split())) for i in range(m)]
LR.sort(key=lambda x: x[1])
s = set()
done = -1
for l,r in LR:
    if done >= l:
        continue
    s.add(r)
    done = r
print(n-len(s))