#include<algorithm>
#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
const int N=4e5+10;
int n,a[N],fa[N];
int siz[N],dep[N],val[N];
int ans=0;
vector<int> e[N];
void dfs(int u,int f) {
	dep[u]=dep[f]+1; siz[u]=1;
	for(int v:e[u]) {
		dfs(v,u);
		siz[u]+=siz[v];
	}
}
int main() {
	scanf("%d",&n);
	for(int i=1; i<=n; i++) scanf("%d",&a[i]);
	for(int i=2; i<=n; i++)
		scanf("%d",&fa[i]),e[fa[i]].push_back(i);
	dfs(1,1);
	for(int i=1; i<=n; i++) val[i]=siz[i]-dep[i]-a[i];
	priority_queue<int> q;
	for(int i=1; i<=n; i++) q.push(val[i]);
	for(; q.size(); ) {
		int x=q.top(); q.pop();
		ans+=x;
		if(q.size()) q.pop();
	}
	printf("%d\n",ans);
	return 0;
}