/*input
7
247522519 398923496 -976223527 806215585 -937536479 -130552271 90576461
1 2 1 2 5 5
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
//#pragma GCC target("avx2")
//order_of_key #of elements less than x
// find_by_order kth element
using ll=long long;
using ld=long double;
using pii=pair<int,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()),c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll maxn=4e5+5;
const ll maxlg=__lg(maxn)+2;
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const int MOD=998244353;
const ld PI=acos(-1);
const ld eps=1e-4;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
    out<<P.f<<' '<<P.s;
    return out;
}
template<typename T>
ostream& operator<<(ostream& out,vector<T> V){
    REP(i,sz(V)) out<<V[i]<<((i!=sz(V)-1)?"\n":"");
    return out;
}
ll mult(ll a,ll b){
    return a*b%MOD;
}
ll mypow(ll a,ll b){
    a%=MOD;
    if(a==0) return 0;
    if(b<=0) return 1;
    ll res=1LL;  
    while(b){
        if(b&1) res=(res*a)%MOD;
        a=(a*a)%MOD;
        b>>=1;
    }
    return res;
}
int arr[maxn];
ll tmp[maxn];
vector<int> v[maxn];
map<vector<ll>,ll> mp;
int n;
ll rec(vector<ll> &vv){
    if(mp.count(vv)){
        return mp[vv];
    }
    vector<int> asd;
    REP(i,n){
        if(vv[i]!=0) asd.pb(i);
    }
    if(sz(asd)==1){
        return vv[asd[0]];
    }
    ll ans=0;
    ll ss=0;
    bool re=0;
    REP(x,n){

        auto tmp=vv;
        bool hv=0;
        if(vv[x]==0){
            int c=0;
            for(int z:v[x]){
                if(tmp[z]) ++c;
            }  
            if(c>=2){
                tmp[x]=-tmp[x];
                for(int z:v[x]){
                    tmp[x]+=tmp[z];
                    tmp[z]=0;
                }
                MXTO(ans,rec(tmp));
                re=1; 
            }
        }
        else{
            if(!hv) tmp[x]=abs(tmp[x]),ss+=tmp[x];
            else{
                tmp[x]=-tmp[x];
                for(int z:v[x]){
                    tmp[x]+=tmp[z];
                    tmp[z]=0;
                }
                MXTO(ans,rec(tmp));
                re=1;
            }
        }
    }
    if(!re) ans=ss;
    return mp[vv]=ans;
}
int main(){
    ios::sync_with_stdio(false),cin.tie(0);
    cin>>n;
    vector<ll> vv;
    REP(i,n){
        cin>>arr[i];
        vv.pb(arr[i]);
    }
    sort(ALL(vv));
    if(vv[0]>0){
        ll ans=-vv[0];
        REP1(i,n-1) ans+=vv[i];
        cout<<ans;
        return 0;
    }
    if(n>7){
        ll ans=0;
        REP(i,n) ans+=abs(arr[i]);
        cout<<ans;
        return 0;
    }
    REP1(i,n-1){
        int p;
        cin>>p;
        --p;
        v[p].pb(i),v[i].pb(p);
    }
    vv.clear();
    REP(i,n) vv.pb(arr[i]);
    cout<<rec(vv);
}