#include<bits/stdc++.h>
#define int long long
using namespace std;
int const M=200200;vector<int>g[M];
int i,n,res,a[M],f[M],dep[M],siz[M];
int read(){
	int x=0;char ch=getchar();
	while (ch<'0'||ch>'9') ch=getchar();
	while (ch>='0'&&ch<='9') x=x*10+ch-48,ch=getchar();
	return x;
} 
void dfs(int x,int fa){
	dep[x]=dep[fa]+1;siz[x]=1;
	for (auto v:g[x])
		dfs(v,x),siz[x]+=siz[v];
}
signed main(){ n=read();
	for (int i=1;i<=n;i++) a[i]=read();
	for (int i=2;i<=n;i++) g[read()].push_back(i);
	dfs(1,0);
	for (int i=1;i<=n;i++) f[i]=siz[i]-dep[i]-a[i];
	sort(f+1,f+1+n,[](int x,int y){return x>y;});
	for (int i=1;i<=n;i++)
		if (i&1) res+=f[i]; 
	return printf("%lld\n",res),0;
}