#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
#define arr(x) array<int, x>
#define scanf(...) assert(scanf(__VA_ARGS__))
using namespace std;
using ll = long long;

const int N = 2e5 + 5;

int n, a[N];

vector<int> vec[N];

int sz[N];

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

int main() {
#ifdef LOCAL
	assert(freopen("test.in", "r", stdin));
	assert(freopen("test.out", "w", stdout));
#endif

	scanf("%d", &n);
	for (int i = 1; i <= n; ++i) {
		scanf("%d", &a[i]);
		a[i] = -a[i];
	}
	for (int i = 2; i <= n; ++i) {
		int x;
		scanf("%d", &x);
		vec[x].push_back(i);
	}
	dfs(1, 1);
	sort(a + 1, a + n + 1);
	ll res = 0;
	for (int i = 1; i <= n; ++i) {
		if ((i & 1) == (n & 1)) {
			res += a[i];
		}
	}
	printf("%lld\n", res);

	return 0;
}