//BZOJ 3697
 //by Cydiater
 //2016.9.26
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <string>
 #include <algorithm>
 #include <queue>
 #include <map>
 #include <ctime>
 #include <cmath>
 #include <iomanip>
 #include <cstdlib>
 using namespace std;
 #define ll long long
 #define up(i,j,n)       for(int i=j;i<=n;i++)
 #define down(i,j,n)     for(int i=j;i>=n;i--)
 ;
 const int oo=0x3f3f3f3f;
 inline int read(){
     ,f=;
     ;ch=getchar();}
     +ch-';ch=getchar();}
     return x*f;
 }
 ,sum,root,siz[MAXN],dis[MAXN],pre[MAXN],deep[MAXN];
 int maxdeep,max_siz[MAXN];
 ll ans=,f[MAXN][],g[MAXN][];
 bool vis[MAXN];
 struct edge{
     int y,next,v;
 }e[MAXN];
 namespace solution{
     inline void insert(int x,int y,int v){e[++len].next=LINK[x];LINK[x]=len;e[len].y=y;e[len].v=v;}
     void init(){
         N=read();
         up(i,,N){
             ll x=read(),y=read(),v=read()==?-:;
             insert(x,y,v);
             insert(y,x,v);
         }
     }
     void make_root(int node,int fa){
         max_siz[node]=;siz[node]=;
         for(int i=LINK[node];i;i=e[i].next)if(!vis[e[i].y]&&e[i].y!=fa){
             make_root(e[i].y,node);
             siz[node]+=siz[e[i].y];
             max_siz[node]=max(max_siz[node],siz[e[i].y]);
         }
         max_siz[node]=max(max_siz[node],sum-max_siz[node]);
         if(max_siz[node]<max_siz[root])root=node;
     }
     void dfs(int node,int father){
         ]++;
         ]++;
         pre[dis[node]]++;
         maxdeep=max(deep[node],maxdeep);
         for(int i=LINK[node];i;i=e[i].next)
             if(e[i].y!=father&&!vis[e[i].y]){
                 deep[e[i].y]=deep[node]+;
                 dis[e[i].y]=dis[node]+e[i].v;
                 dfs(e[i].y,node);
             }
         pre[dis[node]]--;
     }
     void work(int node){
         vis[node]=;g[N][]=;;
         for(int i=LINK[node];i;i=e[i].next)if(!vis[e[i].y]){
             dis[e[i].y]=e[i].v+N;deep[e[i].y]=;maxdeep=;
             dfs(e[i].y,);mx=max(mx,maxdeep);
             ans+=1LL*(g[N][]-)*f[N][];
             up(k,-maxdeep,maxdeep)
                 ans+=1LL*g[N-k][]*f[N+k][]+1LL*g[N-k][]*f[N+k][]+1LL*g[N-k][]*f[N+k][];
             up(j,N-maxdeep,N+maxdeep){
                 g[j][]+=f[j][];
                 g[j][]+=f[j][];
                 f[j][]=f[j][]=;
             }
         }
         up(j,N-mx,N+mx)g[j][]=g[j][]=;
         for(int i=LINK[node];i;i=e[i].next)if(!vis[e[i].y]){
             root=;sum=siz[e[i].y];
             make_root(e[i].y,);
             work(root);
         }
     }
     void slove(){
         sum=N;root=;max_siz[root]=N;
         make_root(,);
         work(root);
     }
     void output(){
         cout<<ans<<endl;
     }
 }
 int main(){
     //freopen("input.in","r",stdin);
     using namespace solution;
     init();
     slove();
     output();
     ;
 }