n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
from bisect import bisect_left
v2i = {a[i]: i for i in range(n)}
c = [v2i[num] for num in b if num in v2i]
d = []
for num in c:
p = bisect_left(d, num)
if p == len(d):
d.append(num)
else:
d[p] = num
print(len(d))