#include <bits/stdc++.h>

using namespace std;

#define rep(i, s, e) for (int i = s; i <= e; ++i)
#define drep(i, s, e) for (int i = s; i >= e; --i)
#define file(a) freopen(#a".in", "r", stdin), freopen(#a".out", "w", stdout)
#define pv(a) cout << #a << " = " << a << endl
#define pa(a, l, r) cout << #a " : "; rep(_, l, r) cout << a[_] << ' '; cout << endl

const int N = 1e6 + 10;

int read() {
  int x = 0, f = 1; char c = getchar();
  for (; c < '0' || c > '9'; c = getchar()) if (c == '-') f = -1;
  for (; c >= '0' && c <= '9'; c = getchar()) x = x * 10 + c - 48;
  return x * f;
}

int n, w[N], p[N], dep[N], sz[N];
vector <int> e[N];
long long ans;

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

int main() {
  n = read();
  rep(i, 1, n) w[i] = read();
  rep(i, 2, n) p[i] = read(), e[p[i]].emplace_back(i);
  dep[1] = 1, dfs(1);
  sort(w + 1, w + n + 1);
  reverse(w + 1, w + n + 1);
  for (int i = 1; i <= n; i += 2) ans += w[i];
  printf("%lld\n", ans);
  return 0;
}