题解 | #排队合影#

import java.util.*;
import java.lang.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        sc.nextLine();
        String[] init = sc.nextLine().split(" ");
        String[] target = sc.nextLine().split(" ");
        System.out.println(myfun(init, target));
    }
    
    static public int myfun(String[] init, String[] target){
        int n = target.length;
        int cnt = 0;
        int i = n-1;
        int j = n-1;
        Set<String> set = new HashSet<>();

        while(i >= 0){
            while(set.contains(target[j])){
                j--;
            }
            if(init[i].equals(target[j])){
                i--;
                j--;
            }else{
                set.add(init[i]);
                i--;
                cnt++;
            }
        }
        return cnt;
    }
}