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

P = [list(map(int, input().split())) for i in range(M)]
P.sort(key = lambda x: x[1])

ans = N
last0 = 0
for i in range(M):
    l, r = P[i]
    if l <= last0 <= r:
        continue
    else:
        last0 = r
        ans -= 1
print(ans)