#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define int long long
#define ull unsigned long long
using namespace std;
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;return x;
}

#define mod 998244353
struct modint{
    int x;
    modint(int o=0){x=o;}
    modint &operator = (int o){return x=o,*this;}
    modint &operator +=(modint o){return x=x+o.x>=mod?x+o.x-mod:x+o.x,*this;}
    modint &operator -=(modint o){return x=x-o.x<0?x-o.x+mod:x-o.x,*this;}
    modint &operator *=(modint o){return x=1ll*x*o.x%mod,*this;}
    modint &operator ^=(int b){
        modint a=*this,c=1;
        for(;b;b>>=1,a*=a)if(b&1)c*=a;
        return x=c.x,*this;
    }
    modint &operator /=(modint o){return *this *=o^=mod-2;}
    friend modint operator +(modint a,modint b){return a+=b;}
    friend modint operator -(modint a,modint b){return a-=b;}
    friend modint operator *(modint a,modint b){return a*=b;}
    friend modint operator /(modint a,modint b){return a/=b;}
    friend modint operator ^(modint a,int b){return a^=b;}
    friend bool operator ==(modint a,int b){return a.x==b;}
    friend bool operator !=(modint a,int b){return a.x!=b;}
    bool operator ! () {return !x;}
    modint operator - () {return x?mod-x:0;}
    bool operator <(const modint&b)const{return x<b.x;}
};
inline modint qpow(modint x,int y){return x^y;}

vector<modint> fac,ifac,iv;
inline void initC(int n)
{
    if(iv.empty())fac=ifac=iv=vector<modint>(2,1);
    int m=iv.size(); ++n;
    if(m>=n)return;
    iv.resize(n),fac.resize(n),ifac.resize(n);
    For(i,m,n-1){
        iv[i]=iv[mod%i]*(mod-mod/i);
        fac[i]=fac[i-1]*i,ifac[i]=ifac[i-1]*iv[i];
    }
}
inline modint C(int n,int m){
    if(m<0||n<m)return 0;
    return initC(n),fac[n]*ifac[m]*ifac[n-m];
}
inline modint sign(int n){return (n&1)?(mod-1):(1);}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair 
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 200005
#define inf 0x3f3f3f3f

int n,fa[maxn],dep[maxn],res,w[maxn],sz[maxn],p[maxn];
vi e[maxn];

void dfs(int u){
    sz[u]=1;
    for(int v:e[u]){
        dep[v]=dep[u]+1;
        dfs(v);
        sz[u]+=sz[v];
    }
}

int col[maxn];
int cnt[maxn];
void solve(int u){
    for(int v:e[u]){
        solve(v);
        cnt[u]+=cnt[v];
    }
    if(col[u]){
        res+=w[u];
        res+=cnt[u];
    }else{
        res-=(sz[u]-1);
        res+=cnt[u];
        cnt[u]++;
    }
}

signed main()
{
    n=read();
    For(i,1,n)w[i]=-read();
    For(i,2,n)fa[i]=read(),e[fa[i]].pb(i);
    dfs(1);
    For(i,1,n)p[i]=i;
    sort(p+1,p+n+1,[&](int x,int y){
        return w[x]+sz[x]-dep[x]>w[y]+sz[y]-dep[y];
    });
    
    For(i,1,n) col[p[i]]=i&1;
//	For(i,1,n) cout<<col[i]<<" ";puts("");
    solve(1);
    cout<<res;
    return 0;
}
/*
7
0 0 1 0 0 0 0
1 1 2 2 3 3
*/