Y HDU - 4705

#pragma comment(linker, "/STACK:1024000000,1024000000") //加栈
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <queue>
#include <map>
#include <vector>
#include <set>
#include <string>
#include <math.h>
#include <stack>
using namespace std;
typedef long long ll;
const int maxn = 1e5+10;
#define inf 0x3f3f3f3f
int n;
int num,cnt[maxn];
int head[maxn];
ll ans;
struct Edge
{
    int u,v,next,w;
}edge[maxn<<1];
void addEdge(int u,int v,int w)
{
    edge[num].u=u;
    edge[num].v=v;
    edge[num].w=w;
    edge[num].next=head[u];
    head[u]=num++;
}
void init()
{
    num=0;
    memset(head,-1,sizeof(head));
}
void dfs(int u,int pre)//dfs求出在同一路径上的点的数量
{
    int tmp=0;
    cnt[u]=1;
    for(int i=head[u];i!=-1;i=edge[i].next)
    {
        int v=edge[i].v;
        if(v==pre) continue;
        dfs(v,u);
        ans+=1ll*tmp*cnt[v];
        cnt[u]+=cnt[v];
        tmp+=cnt[v];
    }
    ans+=1ll*tmp*(n-cnt[u]);
}
int main(int argc, char const *argv[])
{
     #ifndef ONLINE_JUDGE
        freopen("in.txt","r",stdin);
        freopen("out.txt","w",stdout);
    #endif
    while(scanf("%d",&n)!=EOF)
    {
        init();
        for(int i=1;i<n;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            addEdge(x,y,0);
            addEdge(y,x,0);
        }
        memset(cnt,0,sizeof(cnt));
        ans=0;
        dfs(1,0);
        ll res=1ll*n*(n-1)*(n-2)/6;
        cout<<res-ans<<endl;
    }
    return 0;
}