N,M = map(int,input().split())
lsLR = []
for i in range(M):
    L,R = map(int,input().split())
    lsLR.append((L,R))
lsLR.sort(reverse=True)
cnt = 0
ind = 0
while lsLR:
    l,r = lsLR.pop()
    rr = r
    cnt += 1
    while lsLR:
        l,r = lsLR[-1]
        if l <= rr:
            lsLR.pop()
            continue
        else:
            break
print(N-cnt)