Subtask #0 第一个点过了。

#include<bits/stdc++.h>
using namespace std;
int n,m,lg;
long long ans,dep[400001],sum[400001];
int anc[400001][20],in[400001];
long long c1[400001],c2[400001];
vector<int> edge[400001];
void dfs(int u,int father,int dp)
{
	dep[u]=dp;
	anc[u][0]=father;
	in[father]++;
	for(auto v:edge[u])
	{
		if(v==father)
			continue;
		dfs(v,u,dp+1);
	}
	return;
}
int LCA(int u,int v)
{
	if(dep[u]<dep[v])
		swap(u,v);
	int k=lg;
	while(k>=0)
	{
		if(dep[anc[u][k]]>=dep[v])
			u=anc[u][k];
		k--;
	}
	if(u==v)
		return u;
	k=lg;
	while(k>=0)
	{
		if(anc[u][k]!=anc[v][k])
		{
			u=anc[u][k];
			v=anc[v][k];
		}
		k--;
	}
	return anc[u][0];
}
void dfs2(int u,int father)
{
	for(auto v:edge[u])
	{
		if(v==father)
			continue;
		dfs2(v,u);
		sum[u]+=sum[v];
	}
	return;
}
int u[400001],v[400001];
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	while((1<<lg+1)<=n)
		lg++;
	for(int i=1;i<=n-1;i++)
	{
		cin>>u[i]>>v[i]>>c1[i]>>c2[i];
		edge[u[i]].push_back(v[i]);
		edge[v[i]].push_back(u[i]);
	}
	dfs(1,0,1);
	for(int i=1;i<=n-1;i++)
	{
		int x=i,y=i+1;
		sum[x]++;
		sum[y]++;
		sum[LCA(x,y)]-=2;
	}
	dfs2(1,0);
	for(int i=1;i<=n-1;i++)
	{
		if(anc[u[i]][0]==v[i])
			ans+=min(c2[i],c1[i]*sum[u[i]]);
		if(anc[v[i]][0]==u[i])
			ans+=min(c2[i],c1[i]*sum[v[i]]);
	}
	cout<<ans;
	return 0;
}