#include <bits/stdc++.h>   using namespace std;   vector<int> childs[100000 + 1];   long long s[100000 + 1];   int p[100000 + 1];   long long a[100000 + 1];   bool flag = false;   void fill(int v, long long prevsum) {     if (s[v] != -1) {       a[v] = s[v] - prevsum;       if (a[v] < 0) flag = true;       for (int i = 0; i < childs[v].size(); ++i) {         fill(childs[v][i], s[v]);       }     } else {       long long mi = 1000000001;       for (int i = 0; i < childs[v].size(); ++i) {         mi = min(mi, s[childs[v][i]]);       }       if (mi == 1000000001) mi = prevsum;       a[v] = mi - prevsum;       if (a[v] < 0) flag = true;       for (int i = 0; i < childs[v].size(); ++i) {         fill(childs[v][i], mi);       }     }   }   int main() {     int n;     cin >> n;     for (int i = 0; i < n; ++i) {       childs[i].clear();     }     for (int i = 2; i < n + 1; ++i) {       cin >> p[i];       childs[p[i]].push_back(i);     }     for (int i = 1; i < n + 1; ++i) {       cin >> s[i];     }     fill(1, 0);     if (flag)       cout << -1 << endl;     else {       long long sum = 0;       for (int i = 1; i < n + 1; ++i) {         sum += a[i];       }       cout << sum << endl;     }   }   