from bisect import*
(n,),*e=[[*map(int,s.split())]for s in open(0)]
p=[0]
for r,R in sorted(e):
  i=bisect_right(p,r)-1
  if 0<=i<len(p):
    p[i]=R
  else:
    insort(p,R)
print(len(p)-1)