#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
long long n,ans,a1[100010],a2[100010],dp1[100010],dp2[100010];
int main(){
	scanf("%lld",&n);
	for(long long i=1;i<=n;i++){
		scanf("%lld",&a1[i]);
		dp1[a1[i]]=i;
	}
	for(long long i=1;i<=n;i++)scanf("%lld",&a2[i]);
	for(long long i=1;i<=n;i++){
		if(dp1[a2[i]]>dp2[ans])dp1[++ans]=dp2[a2[i]];
		else{
			int l=0,r=ans,mid=0;
			while(l<r){
				mid=(l+r)/2;
				if(dp1[mid]<=dp2[a2[i]])l=mid+1;
				else r=mid;
			}
			dp2[l]=min(dp1[a2[i]],dp2[l]);
		}
	}
	printf("%lld",ans);
	return 0;
}