#include<algorithm>

#include<cstdio>

#include<cmath>

#include<cstring>

#include<iostream>

int q[],a[],b[],n,p[],s[][];

int find(int x){

    int l=,r=q[],ans;

    if (x<=q[]) return ;

    while (l<=r){

        int mid=(l+r)/;

        if (q[mid]<x) ans=mid,l=mid+;

        else r=mid-;

    }

    if (q[ans+]<x) return ans+;

    return ans;

}

int main(){

    scanf("%d",&n);

    for (int i=;i<=*n;i++) scanf("%d",&a[i]);

    for (int j=;j<=*n;j++) scanf("%d",&b[j]);

    for (int i=;i<=*n;i++){

        for (int j=;j<=;j++)

         if (s[b[i]][j]==){

                s[b[i]][j]=i;

                break;

         }

    }

    for (int i=;i<=*n;i++){

        int t=a[i];

        for (int j=;j>=;j--) p[++p[]]=s[t][j];

    }

    q[]=;

    q[]=p[];

    for (int i=;i<=p[];i++){

        if (p[i]>q[q[]]) q[++q[]]=p[i];

        else{

            int t=find(p[i]);

            q[t+]=p[i];

        }

    }

    printf("%d\n",q[]);

}