#include<iostream>
#include<cstring>
#include<vector>
#include<set>
#include<queue>
#include<array>
using namespace std;
using LL = long long;
const int maxn = 5e5 + 5;
int p[maxn], sz[maxn], fa[maxn];
vector<int> g[maxn];
LL w[maxn];

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

void merge(int x, int y){
    x = find(x), y = find(y);
    if (x != y){
        p[x] = y;
        sz[y] += sz[x];
        return;
    }
}

struct Node{
    LL sum, sz; int id;

    bool operator<(const Node &t) const {
        return sum * t.sz > t.sum * sz;
    }
};


int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int n;
    cin >> n;
    for(int i = 0; i <= n; i++){
        p[i] = i;
        sz[i] = 1;
    }
    for(int i = 1; i <= n; i++){
        int x;
        cin >> x;
        fa[i] = x;
        g[x].push_back(i);
        merge(x, i);
    }
    if (sz[find(0)] != n + 1){
        cout << -1 << '\n';
        return 0;
    }
    for(int i = 0; i <= n; i++) sz[i] = 1;
    priority_queue<Node> q;
    LL ans = 0;
    for(int i = 1; i <= n; i++){
        cin >> w[i];
        sz[i] = 1;
        q.push({w[i], 1, i});
    } 
    sz[0] = 1;
    for(int i = 0; i <= n; i++){
        p[i] = i;
    }
    while(!q.empty()){
        auto [sum, s, x] = q.top();
        q.pop();
        if (s != sz[find(x)]) continue;
        int t = find(fa[x]);
        ans += sum * sz[t];
        w[t] += w[x];
        sz[t] += sz[x];
        p[x] = t;
        if (t) q.push({w[t], sz[t], t});
    }
    cout << ans << '\n';

}