#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mk make_pair
#define fir first
#define sec second
const int MX = 4e6 + 7,inf = 1e9;
ll val[MX],dep[MX];ll ans = 0;
vector<pair<int,ll > > g[MX];
int pool[MX],top = 0;
struct node{int l,r;ll x;}s[MX];
int rA[MX],rB[MX];
int newnode(int x){int cur = pool[top];top--;s[cur].x = x;s[cur].l = s[cur].r = 0;return cur;}
int merge(int x,int y){
	if(!x || !y)return x | y;
	if(s[x].x > s[y].x)swap(x,y);
	if(rand() & 1)swap(s[x].l,s[x].r);
	s[x].r = merge(s[x].r,y);
	return x;
}

void solve(int x,int f){
	if(val[x] > 0)for(int i = 1;i <= val[x];i++)rA[x] = merge(rA[x],newnode(dep[x]));
	else for(int i = 1;i <= -val[x];i++)rB[x] = merge(rB[x],newnode(dep[x] - inf));
	for(auto it : g[x]){
		int to = it.fir;ll w = it.sec;
		if(f == to)continue;
		dep[to] = dep[x] + w;solve(to,x);rA[x] = merge(rA[x],rA[to]);rB[x] = merge(rB[x],rB[to]);
	}
	while(rA[x] && rB[x] && s[rA[x]].x + s[rB[x]].x - 2 * dep[x] < 0){
		ll u = s[rA[x]].x,v = s[rB[x]].x;ans += s[rA[x]].x + s[rB[x]].x - 2 * dep[x];
		pool[++top] = rA[x];pool[++top] = rB[x];
		rA[x] = merge(s[rA[x]].l,s[rA[x]].r);rB[x] = merge(s[rB[x]].l,s[rB[x]].r);
		rA[x] = merge(rA[x],newnode(2 * dep[x] - v));rB[x] = merge(rB[x],newnode(2 * dep[x] - u));
	}
}
int main(){
	ios :: sync_with_stdio(false);
	for(int i = 1;i < MX;i++){pool[i] = i;top = i;}
	int n;cin >> n;
	for(int i = 1;i < n;i++){int u,v;ll w;cin >> u >> v >> w;g[u].push_back(mk(v,w));g[v].push_back(mk(u,w));}
	for(int i = 1;i <= n;i++){int x,y;cin >> x >> y;val[i] = x - y;}
	for(int i = 1;i <= n;i++)if(val[i] < 0)ans += inf * -val[i];
	solve(1,1);
	cout << ans << '\n';
	return 0;
}