#include <iostream>
#include <cstring>
#include <cmath>

using namespace std;

const int N=550;
typedef long long LL;

LL g[N][N];
LL dist[N];
bool st[N];

LL n,m,res;

void prim()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;
    for(int i=0;i<n;i++)
    {
        int t=-1;
        for(int j=1;j<=n;j++)
        {
            if(!st[j]&&(t==-1||dist[j]<dist[t])) t=j;
        }
        st[t]=true;
        res+=dist[t];
        for(int j=1;j<=n;j++)
        {
            if(!st[j]&&dist[j]>g[t][j])
            {
                dist[j]=g[t][j];
            }
        }
    }
}

int main()
{
    scanf("%lld",&n);
    
    m=2*n-1;

    memset(g,0x3f,sizeof g);
    
    while(m--)
    {
        LL a,b,c,d;
        scanf("%lld%lld%lld%lld",&a,&b,&c,&d);
        if(d==1)
        {
            g[a][b]=g[b][a]=0;
        }
        else
        {
            g[a][b]=g[b][a]=c;
        }
    }
    
    prim();
    
    printf("%lld",res);
    
    return 0;
}