// Problem: P6943 [ICPC2018 WF] Conquer The World
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P6943
// Memory Limit: 1 MB
// Time Limit: 8000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
#include <ext/pb_ds/priority_queue.hpp>
#define pb emplace_back
#define fst first
#define scd second
#define mkp make_pair
#define mems(a, x) memset((a), (x), sizeof(a))

using namespace std;
typedef long long ll;
typedef double db;
typedef unsigned long long ull;
typedef long double ldb;
typedef pair<ll, ll> pii;

const int maxn = 250100;
const ll inf = 1e12;

ll n, dep[maxn], a[maxn], ans;
vector<pii> G[maxn];
__gnu_pbds::priority_queue< ll, greater<ll> > A[maxn], B[maxn];

void dfs(int u, int fa) {
	if (a[u] < 0) {
		for (int _ = 0; _ < -a[u]; ++_) {
			A[u].push(dep[u] - inf);
		}
	} else if (a[u] > 0) {
		for (int _ = 0; _ < a[u]; ++_) {
			B[u].push(dep[u]);
		}
	}
	for (pii p : G[u]) {
		ll v = p.fst, d = p.scd;
		if (v == fa) {
			continue;
		}
		dep[v] = dep[u] + d;
		dfs(v, u);
		A[u].join(A[v]);
		B[u].join(B[v]);
	}
	while (A[u].size() && B[u].size() && A[u].top() + B[u].top() - dep[u] * 2 < 0) {
		ll x = A[u].top(), y = B[u].top();
		A[u].pop();
		B[u].pop();
		ans += x + y - dep[u] * 2;
		A[u].push(dep[u] * 2 - y);
		B[u].push(dep[u] * 2 - x);
	}
}

void solve() {
	scanf("%lld", &n);
	for (int i = 1, u, v, d; i < n; ++i) {
		scanf("%d%d%d", &u, &v, &d);
		G[u].pb(v, d);
		G[v].pb(u, d);
	}
	ll s = 0;
	for (int i = 1, x, y; i <= n; ++i) {
		scanf("%d%d", &x, &y);
		a[i] = x - y;
		if (a[i] < 0) {
			s -= a[i];
		}
	}
	dfs(1, -1);
	printf("%lld\n", ans + s * inf);
}

int main() {
	int T = 1;
	// scanf("%d", &T);
	while (T--) {
		solve();
	}
	return 0;
}