#include<bits/stdc++.h>
using namespace std;

#define cout cerr
#define rep(i,a,b) for(int i=(a);i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>=(b);--i)

typedef long long ll;
typedef pair<int,int> pii;
#define FR first
#define SE second
const ll inf=1e18;

inline void rd(int &x){
    x=0;char ch=getchar();int f=1;
    while(ch<'0'||ch>'9'){
        if(ch=='-')f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        x=x*10+ch-'0';
        ch=getchar();
    }
    x*=f;
}
//是否解决 系数 类型

int n;
#define Maxn 400010
int a[Maxn];
ll F[Maxn][8];
int head[Maxn],v[Maxn],nxt[Maxn],tot=0;
void add_edge(int s,int e){
    tot++;v[tot]=e;nxt[tot]=head[s];head[s]=tot;
}

int calc(int a,int b){
    int a1=(a/2)&1,a2=a/4;
    int b1=(b/2)&1,b2=b/4;
    if(a2==1&&b2==1)return -1;
    if(a2==0&&b2==0)return 0;
    if(a2==0&&b2==1&&a1!=b1)return 1;
    if(a2==1&&b2==0&&a1!=b1)return 2;
    return 0;
}

ll fjz[8];
void dfs(int u){
    rep(i,0,7)
    if(i!=1&&i!=3){
        int t=(i/2)&1;
        if(t==0)F[u][i]=a[u];
        else F[u][i]=-a[u];
    }else F[u][i]=-inf;
    for(int i=head[u];i;i=nxt[i]){
        int t=v[i];
        dfs(t);
        rep(j,0,7)fjz[j]=-inf;
        rep(c1,0,7)
            rep(c2,0,7){
                int cur=calc(c1,c2);
                if(cur==-1)continue;
                int ss=c2&1;
                if(cur==2)ss=1;
                if(ss==0)continue;
                int tmp=c1;
                if(cur==1)tmp|=1;
                fjz[tmp]=max(fjz[tmp],F[u][c1]+F[t][c2]);
            }
        rep(j,0,7)F[u][j]=fjz[j];
    }
}

int main(){
    rd(n);
    rep(i,1,n)rd(a[i]);
    rep(i,2,n){
        int x;rd(x);add_edge(x,i);
    }
    dfs(1);ll Ans=-inf;
    for(int i=1;i<=7;i+=2)Ans=max(Ans,F[1][i]);
    printf("%lld\n",Ans);
    return 0;
}