N=int(input())
P=list(map(int,input().split()))
Q=list(map(int,input().split()))

A=[(P[i],i) for i in range(N)]
A.sort()

B=[-1]*N
for i in range(N):
    B[A[Q[i]-1][1]]=i+1

B_INV=[-1]*N
for i in range(N):
    B_INV[B[i]-1]=i

block=0
for i in range(N-1):
    if B_INV[i]>B_INV[i+1]:
        block+=1

ANS=0
while block:
    ANS+=1
    block//=2

print(ANS)