//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
ll d[500500];
int p[500500],n;
vector<int> G[500500];
ll f[500500][2],g[500500][2],h[500500];
void dfs(int u)
{
	for(auto v:G[u])
		dfs(v);
	ll tmp[2]={0,0};
	for(auto v:G[u])
	{
		ll w0=max({f[v][0],f[v][1],h[u]});
		ll w1=max(f[v][0]-d[u],f[v][1]+d[u]);
		tmp[1]=max(tmp[1]+w0,tmp[0]+w1);
		tmp[0]+=w0;
	}
	h[u]=tmp[1];
	for(auto v:G[u])
	{
		f[u][0]+=g[v][0];
		f[u][1]+=g[v][1];
	}
	f[u][0]+=d[u];
	f[u][1]-=d[u];
	g[u][0]=max(tmp[1],tmp[0]-d[u]);
	g[u][1]=max(tmp[1],tmp[0]+d[u]);
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>d[i];
	for(int i=2;i<=n;i++)
		cin>>p[i];
	for(int i=2;i<=n;i++)
		G[p[i]].pb(i);
	dfs(1);
	cout<<h[1]<<endl;
	return 0;
}