N = int(input())
B = list(map(int,input().split()))
A = list(map(int,input().split()))

C = {a:i for i,a in enumerate(A)}

B = [C[b] for b in B]

now = set()
#print(B)
for b in B:
    if b-1 in now:
        now.add(b)
        now.remove(b-1)
    else:
        now.add(b)

n = len(now)
ans = 0
while n>1:
    n = (n+1)//2
    ans += 1
print(ans)