#include<bits/stdc++.h>

 using namespace std;

 typedef long long ll;

 ll read()

 {

    ll x=,f=;char ch=getchar();

    while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}

    while (ch>=''&&ch<='') x=(x<<)+(x<<)+ch-'',ch=getchar();

    return x*f;

 }

 const int N=;

 vector<ll> vec[N];

 ll ans,sum[N],he[N],cnt,head[N],n,a[N],fa[N],w[N],sz[N],cn,vis[N],tail[N],f[N];

 int find(int x){return x==f[x]?x:f[x]=find(f[x]);}

 struct _node{ll sum,he,sz,id;_node(ll A,ll B,ll C,ll D){sum=A;he=B;sz=C;id=D;}};

 struct cmp{

     bool operator () (const _node &A,const _node &B)

     {return A.he*B.sz>B.he*A.sz||A.he*B.sz==B.he*A.sz&&A.sz<B.sz;}

 };

 priority_queue<_node,vector<_node>,cmp> q;

 int main()

 {

     n=read();

     for (int i=;i<=n;i++) f[i]=i;

     for (int i=;i<=n;i++)

     {

         a[i]=read();

         if (<a[i]&&a[i]<=n) vec[a[i]].push_back(i),fa[i]=a[i]; else fa[i]=-;

     }

     for (int i=;i<=n;i++) w[i]=read(),q.push(_node(sum[i]=w[i],he[i]=w[i],sz[i]=,i));

     while (!q.empty())

     {

         int x=q.top().id,fx=fa[find(x)];q.pop();

         if (vis[x]) continue; vis[x]=; //dijkstra的思想，肯定先访问最后一次合并过的点，其他过去版本直接continue，这样就不用再记录一个del的堆。

        if (fx==-)

        {

            ans+=sum[x]+cn*he[x];

            for (int i=;i<vec[x].size();i++)  fa[vec[x][i]]=-;

            cn+=sz[x];

         }

        else {

            if (vis[fx]) return puts("-1"),;

            for (int i=;i<vec[x].size();i++) f[vec[x][i]]=find(x);

            sum[fx]+=sum[x]+he[x]*sz[fx];he[fx]+=he[x];sz[fx]+=sz[x];

            q.push(_node(sum[fx],he[fx],sz[fx],fx));

         }

     }

     printf("%lld\n",ans);

    return ;

 }