//贺的 wlxhkk 神仙的 [双手合十] 

#include <iostream>
#include <cstdio>

#define maxn 355555
#define inf 0x3f3f3f3f3f3f3f3f
#define int long long

using namespace std;

inline int read(){
	int x = 0, flag = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9'){
		if(ch == '-') flag = -1;
		ch = getchar();
	}
	while(ch >= '0' && ch <= '9'){
		x = (x << 3) + (x << 1) + ch - '0';
		ch = getchar();
	}
	return x * flag;
}

int hd[maxn], cnt;
struct edge{
	int v, nxt;
}e[maxn << 1];
void add(int u, int v){
	e[++cnt].v = v;
	e[cnt].nxt = hd[u];
	hd[u] = cnt;
	return;
}

int max(int x, int y, int z){
	return max(max(x, y), z);
}

int n, f[maxn][3][2], g[3][2], a[maxn], tmp;
//结局 儿子 | 自己 | 父亲
//父亲有没有被选。
//考虑中间这次。

void dfs(int u, int fa){
	for(int i = hd[u]; i; i = e[i].nxt){
		int v = e[i].v;
		dfs(v, u);
	}
	for(int i = 0; i <= 2; ++i)
		for(int j = 0; j <= 1; ++j)
			g[i][j] = 0;
	tmp = 0;
	g[0][0] = -inf;
	g[1][0] = -a[u];
	for(int i = hd[u]; i; i = e[i].nxt){
		int v = e[i].v;
		g[0][0] = max(g[0][0] + max(f[v][0][0], f[v][1][0], f[v][2][0] + a[v]), tmp + max(f[v][0][1], f[v][2][1]));
		tmp += max(f[v][0][0], f[v][1][0], f[v][2][0] + a[v]);
		g[1][0] += max(f[v][2][0] + a[v], f[v][0][0]);
		g[2][0] += max(f[v][2][0] + a[v], f[v][1][0], f[v][0][0]);
	}
	g[0][1] = g[0][0] + a[fa];
	g[1][1] = g[1][0] + a[fa];
	for(int i = 0; i <= 2; ++i)
		for(int j = 0; j <= 1; ++j)
			f[u][i][j] = g[i][j], g[i][j] = 0;
	tmp = 0;
	g[0][0] = -inf;
	g[1][0] = a[u];
	for(int i = hd[u]; i; i = e[i].nxt){
		int v = e[i].v;
		g[0][0] = max(g[0][0] + max(f[v][0][0], f[v][1][0], f[v][2][0] - a[v]), tmp + max(f[v][0][1], f[v][2][1]));
		tmp += max(f[v][0][0], f[v][1][0], f[v][2][0] - a[v]);
		g[1][0] += max(f[v][2][0] - a[v], f[v][0][0]);
		g[2][0] += max(f[v][2][0] - a[v], f[v][1][0], f[v][0][0]);
	}
	g[0][1] = g[0][0] - a[fa];
	g[1][1] = g[1][0] - a[fa];
	for(int i = 0; i <= 2; ++i)
		for(int j = 0; j <= 1; ++j)
			f[u][i][j] = max(f[u][i][j], g[i][j]);
	return;
}

signed main(){
	n = read();
	for(int i = 1; i <= n; ++i) a[i] = read();
	for(int i = 2; i <= n; ++i){
		int p = read();
		add(p, i);
	}
	dfs(1, 0);
	printf("%lld", max(f[1][0][0], f[1][1][0]));
	return 0;
}