#include <bits/stdc++.h>
const int MAXN=1e5+10;
#define ll long long
using namespace std;
int ch[MAXN][2],res[MAXN],pre[MAXN];bool rt[MAXN];
ll size1[MAXN],size[MAXN];int st[MAXN],tp;
typedef struct node{
int u,v;ll vul;
}node;
node d[MAXN];
ll readll(){
ll x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int readint(){
int x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return f*x;
}
void update_res(int r){
if(!r) return ;
swap(ch[r][0],ch[r][1]);
res[r]^=1;
}
void push(int x){
if(res[x]){
update_res(ch[x][0]);
update_res(ch[x][1]);
res[x]^=1;
}
}
void up(int x){
size[x]=size[ch[x][0]]+size[ch[x][1]]+size1[x]+1;
}
bool pd(int x){
return ch[pre[x]][0]!=x&&ch[pre[x]][1]!=x;
}
void P(int x){
int i;st[++tp]=x;
for(i=x;!pd(i);i=pre[i]) st[++tp]=pre[i];
for(;tp;tp--) push(st[tp]);
}
void rotate(int x,int kind){
int y=pre[x];
ch[y][!kind]=ch[x][kind];pre[ch[x][kind]]=y;
if(rt[y]) rt[x]=1,rt[y]=0;
else ch[pre[y]][ch[pre[y]][1]==y]=x;
pre[x]=pre[y];ch[x][kind]=y;pre[y]=x;
up(y);
}
void splay(int x){
P(x);
while(!rt[x]){
if(rt[pre[x]]) rotate(x,ch[pre[x]][0]==x);
else{
int y=pre[x];int kind=ch[pre[y]][0]==y;
if(ch[y][kind]==x) rotate(x,!kind),rotate(x,kind);
else rotate(y,kind),rotate(x,kind);
}
}
up(x);
}
void access(int x){
int y=0;
while(x){
splay(x);
if(ch[x][1]) rt[ch[x][1]]=1,size1[x]+=size[ch[x][1]],pre[ch[x][1]]=x;
if(y) rt[y]=0,size1[x]-=size[y];ch[x][1]=y;up(x);
y=x;x=pre[x];
}
}
void mroot(int u){
access(u);splay(u);update_res(u);
}
void Link(int u,int v){
mroot(u);mroot(v);
pre[u]=v;size1[v]+=size[u];size[v]+=size[u];
}
ll querty(int u,int v,ll vul){
mroot(u);access(v);splay(v);
ll t=1ll*size[u]*(size[v]-size[u])*vul;
pre[v]=pre[u]=0;rt[v]=rt[u]=1;ch[v][0]=0;
up(u);up(v);
return t;
}
void newnode(int v){
pre[v]=size1[v]=ch[v][0]=ch[v][1]=res[v]=0;rt[v]=1;size[v]=1;
}
bool cmp1(node aa,node bb){
return aa.vul>bb.vul;
}
bool cmp2(node aa,node bb){
return aa.vul<bb.vul;
}
int main(){
int n;
while(scanf("%d",&n)!=EOF){
// inte();
for(int i=1;i<n;i++) d[i].u=readint(),d[i].v=readint(),d[i].vul=readint();
for(int i=1;i<=n;i++) newnode(i);
for(int i=1;i<n;i++) Link(d[i].u,d[i].v);
ll sum1=0;
sort(d+1,d+n,cmp1);
for(int i=1;i<n;i++) sum1+=querty(d[i].u,d[i].v,d[i].vul);
//inte();
for(int i=1;i<=n;i++) newnode(i);
for(int i=1;i<n;i++) Link(d[i].u,d[i].v);
sort(d+1,d+n,cmp2);
for(int i=1;i<n;i++) sum1-=querty(d[i].u,d[i].v,d[i].vul);
printf("%lld\n",sum1);
}
return 0;
}
