#include<bits/stdc++.h>
#define F(i,l,r) for(int i=(l),i##end=(r);i<=i##end;++i)
#define G(i,l,r) for(int i=(l),i##end=(r);i>=i##end;--i)
#define pii pair<int,int>
#define x first
#define y second
#define mp(x,y) make_pair(x,y)
#define ep emplace_back
using namespace std;
typedef long long ll;
constexpr int N=2e5;
int fa[N+9],dep[N+9],sz[N+9];
int w[N+9],id[N+9];
vector<int> E[N+9];
void dfs(int x)
{
	for(auto u:E[x])
	{
		dep[u]=dep[x]+1;
		dfs(u);
		sz[x]+=sz[u]+1;
	}
}
int main()
{
	cin.tie(0)->sync_with_stdio(false);
	int n;
	cin>>n;
	F(i,1,n)cin>>w[i],id[i]=i;
	F(i,2,n)cin>>fa[i],E[fa[i]].ep(i);
	dfs(1);
	sort(id+1,id+n+1,[](int a,int b){return sz[a]-w[a]-dep[a]>sz[b]-w[b]-dep[b];});
	ll ans=0;
	F(i,1,n)if(i&1)ans+=sz[id[i]]-w[id[i]]-dep[id[i]];
	cout<<ans<<'\n';
	return 0;
}