#include <bits/stdc++.h>
using namespace std;
#define int long long
int n, dummy, root, ans=INT_MIN;
vector < vector < int > > adj; vector < int > value;
 
void solve(int node, int maxval)
{
	maxval=max(maxval, value[node]);
	ans=max(ans, maxval-value[node]);
	for (int i=0; i<adj[node].size(); i++) solve(adj[node][i], maxval);
}
 
signed main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n;
	adj.resize(n+1);
	value.resize(n+1);
	for (int i=1; i<=n; i++) cin >> value[i];
	for (int i=1; i<=n; i++)
	{
		cin >> dummy;
		if (dummy==-1) root=i;
		else adj[dummy].push_back(i);
	}
	solve(root, value[root]);
	cout << ans;
}

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