#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int n, w[N], u, dep[N], siz[N]; basic_string <int> son[N]; long long ans;
void dfs(int u) {
	dep[u] ++, siz[u] = 1;
	for (int v : son[u])
		dep[v] = dep[u], dfs(v), siz[u] += siz[v];
	w[u] = siz[u] - dep[u] - w[u];
}
int main() {
	cin >> n;
	for (int i=1; i<=n; i++)
		scanf ("%d", &w[i]);
	for (int i=2; i<=n; i++)
		scanf ("%d", &u), son[u] += i;
	dfs(1), sort (w+1, w+n+1);
	for (int i=n; i>0; i-=2)
		ans += w[i];
	cout << ans;
}