#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
typedef long long ll;
#define SZ(a) (int)(a).size()
 
int main() {
	cin.sync_with_stdio(false);
	int n;
	cin >> n;
	vector<int> h(n);
	for (int i = 0; i < n; i++) {
		int x;
		cin >> x;
		x--;
		h[x] = i;
	}
	int prv = -2;
	int ans = n;
	for (int i = 0; i < n; i++) {
		int x;
		cin >> x;
		x--;
		auto cur = h[x];
		if (cur == prv+1) {
			ans--;
		}
		prv = cur;
	}
	printf("%d\n", ans);
	return 0;
}
 

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