#include<bits/stdc++.h>
using namespace std;
const int NR=3e5+10;
#define int long long
int n,a[NR],dep[NR],val[NR],sum[NR],idx[NR],ans;
#define pii pair<int,int>
#define fi first
#define se second
#define mkp make_pair
vector<pii>g[NR];
#define pb emplace_back
priority_queue<int,vector<int>,greater<int> >q1[NR],q2[NR];

void merge(int &x,int y,int d){
	if(sum[x]<sum[y])swap(x,y);
	while(!q1[y].empty())q1[x].push(q1[y].top()),q1[y].pop(); 
	while(!q2[y].empty())q2[x].push(q2[y].top()),q2[y].pop();
	sum[x]+=sum[y];
}
const int inf=1e12;
void dfs(int id,int fath){
	idx[id]=id;sum[id]=abs(val[id]);
	if(val[id]>0){
		for(int i=1;i<=val[id];i++)q2[id].push(dep[id]);
	}
	if(val[id]<0){
		for(int i=1;i<=-val[id];i++)q1[id].push(dep[id]-inf);
	}
	for(auto lcy:g[id])
		if(lcy.fi!=fath){
			dep[lcy.fi]=dep[id]+lcy.se;
			dfs(lcy.fi,id);
			merge(idx[id],idx[lcy.fi],dep[id]);
		}
	while(!q1[idx[id]].empty()&&!q2[idx[id]].empty()&&q1[idx[id]].top()+q2[idx[id]].top()-2*dep[id]<0){
		int v1=q1[idx[id]].top(),v2=q2[idx[id]].top();
//		cout<<v1<<" "<<v2<<" "<<dep[id]<<endl;
		q1[idx[id]].pop(),q2[idx[id]].pop();
		ans+=v1+v2-2*dep[id];
		q1[idx[id]].push(2*dep[id]-v2),q2[idx[id]].push(2*dep[id]-v1);
	}
}

signed main(){
	cin>>n;
	for(int i=1,x,y,z;i<n;i++)
		cin>>x>>y>>z,g[x].pb(mkp(y,z)),g[y].pb(mkp(x,z));
	for(int i=1,x,y;i<=n;i++)
		cin>>x>>y,val[i]=x-y;
	dfs(1,0);
	int res=0;
	for(int i=1;i<=n;i++)res+=max(0ll,-val[i]);
	cout<<ans+inf*res<<endl;
	return 0;
}