# include<bits/stdc++.h>
# define LL long long
using namespace std;
vector<int> link[1000010];
LL w[1000010];
int dep[1000010],sz[1000010];
void dfs(int fa,int p){
    dep[p]=dep[fa]+1;
    for (int i=0;i<link[p].size();i++){
        int q=link[p][i];
        if (q==fa) continue;
        dfs(p,q);
        sz[p]+=sz[q];
    }
    sz[p]+=1;
}
int main(){
    std::ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int n;cin>>n;
    for (int i=1;i<=n;i++) cin>>w[i];
    for (int i=2;i<=n;i++){
        int x;cin>>x;
        link[x].push_back(i);
    }
    dfs(0,1);
    for (int i=1;i<=n;i++){
        w[i]=-w[i]+(sz[i]-1)-(dep[i]-1);
    }
    sort(w+1,w+n+1);
    LL ans=0;
    for (int i=n;i>=1;i-=2){
        ans+=w[i];
    }
    cout<<ans;
}
/*
7
0 0 1 0 0 0 0
1 1 2 2 3 3
*/