#include <bits/stdc++.h>
using namespace std;
#define int long long
namespace IO {
	#if ONLINE_JUDGE
	#define getc() (IS == IT && (IT = (IS = ibuf) + fread(ibuf, 1, IL, stdin), IS == IT) ? EOF : *IS++)
	#else
	#define getc() getchar()
	#endif
	const int IL = 1 << 21, OL = 1 << 21;
	int olen = 0;
	char ibuf[IL], *IS = ibuf, *IT = ibuf, obuf[OL];
	inline int read() {
		register char ch = getc(); register int x = 0, f = 1;
		while(!isdigit(ch)) { if(ch == '-') f = -1; ch = getc(); }
		while(isdigit(ch)) x = x * 10 + ch - 48, ch = getc();
		return x * f;
	}
	inline double readdb() {
		register char ch = getc(); register double x = 0, f = 1;
		while(!isdigit(ch)) { if(ch == '-') f = -1; ch = getc(); }
		while(isdigit(ch)) x = x * 10 + ch - 48, ch = getc();
		if(ch == '.') {
			register double b = 0.1;
			ch = getc();
			while(isdigit(ch)) x += (ch - 48) * b, b *= 0.1, ch = getc();
		}
		return x * f;
	}
	inline int readstr(char *s) {
		register char ch = getc(); register int len = 0;
		while(!isalpha(ch)) ch = getc();
		while(isalpha(ch)) s[++len] = ch, ch = getc();
		return len;
	}
	inline void flush() { fwrite(obuf, 1, olen, stdout); olen = 0; }
	inline void putc(register char ch) { obuf[olen++] = ch; }
	template<class T>
	inline void write(register T x) {
		if(x < 0) obuf[olen++] = '-', x = -x;
		if(x > 9) write(x / 10);
		obuf[olen++] = x % 10 + 48;
	}
} using namespace IO;
const int N = 2e5 + 10;
int n, w[N], dep[N], siz[N];
vector<int> e[N];
void dfs(int u, int f) {
	dep[u] = dep[f] + 1, siz[u] = 1;
	for(auto v : e[u])
		dfs(v, u), siz[u] += siz[v];
}
signed main() {
	n = read();
	for(int i = 1; i <= n; i++)
		w[i] = read();
	for(int i = 2, f; i <= n; i++) {
		f = read();
		e[f].push_back(i);
	}
	dfs(1, 0);
	for(int i = 1; i <= n; i++)
		w[i] = siz[i] - w[i] - dep[i];
	sort(w + 1, w + 1 + n, greater<int>());
	int ans = 0;
	for(int i = 1; i <= n; i += 2) ans += w[i];
	printf("%lld", ans);
	return 0;
}