#include<bits/stdc++.h>
using namespace std;
int n, ans[1005];
vector<int> G[1005];
int pos[3][1005], res;
int dfs(int x){
	if(ans[x])
		return ans[x];
	ans[x] = 1;
	for(int i: G[x])
		ans[x] = max(dfs(i) + 1, ans[x]);
	return ans[x];
}signed main(){
	scanf("%d", &n);
	for(int i = 1; i <= 2; ++i){
		for(int j = 1; j <= n; ++j){
			int a;
			scanf("%d", &a);
			pos[i][a] = j;
		}
	}for(int j = 1; j <= n; ++j){
		for(int l = 1; l <= n; ++l){
			for(int i = 1; i <= 2; ++i){
				if(pos[i][j] >= pos[i][l])
					break;
				if(i == 2)
					G[j].push_back(l);
			}
		}
	}for(int i = 1; i <= n; ++i)
		res = max(res, dfs(i));
	printf("%d", res);
	return 0;
}