#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
#define LL long long
using namespace std;

#define L(i, s, t) for(int i = s; i <= t; ++i)
#define R(i, t, s) for(int i = t; i >= s; --i)

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

const int N = 1e5;

int n, fa[N + 5], c[N + 5], dep[N + 5], sz[N + 5];
int h[N + 5], nxt[2 * N + 5], e[2 * N + 5];
priority_queue<int > q[N + 5]; LL ans;
void dfs(int x, int ff) {
	q[x].push(c[x]); sz[x] = 1;
	int son = -1;
	for(int i = h[x]; i; i = nxt[i]) {
		int v = e[i];
		if (v == ff) continue;
		dfs(v, x);
		if (son == -1 || sz[v] > sz[son])
			son = v;
		sz[x] += sz[v];
	}
	if (son != -1) swap(q[x], q[son]);
	for(int i = h[x]; i; i = nxt[i]) {
		int v = e[i];
		if (v == ff) continue;
		while(!q[v].empty()) {q[x].push(q[v].top()); q[v].pop();}
	}
	// if (x == 3) cout << c[x] << ' ' << q[x].top() << endl;
	if (c[x] < q[x].top()) {
		ans += q[x].top() - c[x];
		q[x].pop();
		q[x].push(c[x]);
	}
	// q[x].push(c[x]);

}

int tot;
void add(int x, int y) {nxt[++tot] = h[x]; e[tot] = y; h[x] = tot;}

int main() {
	// freopen("t.in", "r", stdin);
	// q[1].pop();
	read(n); read(c[1]); 
	for(int i = 2; i <= n; ++i)
		{read(fa[i]); dep[i] = dep[fa[i]] + 1; read(c[i]); c[i] += dep[i];
		 add(i, fa[i]); add(fa[i], i);
		}
	dfs(1, 0);
	printf("%lld\n", ans);
    return 0;
}