from bisect import bisect_left, bisect_right
N = int(input())
LR = [tuple(map(int, input().split())) for _ in range(N)]
LR.sort(key=lambda x: x[1], reverse=True)

Q = []
while LR:
   l, r = LR.pop()
   j = bisect_right(Q, l)
   if j == 0:
      Q.append(r)
   else:
      Q[j-1] = r

ans = len(Q) - 1
print(ans)