#include <bits/stdc++.h>
using namespace std;
const int MX=100100;
int n,i,cur,now,xc,yc,it,x[MX],y[MX],k[MX],nx[MX],ny[MX],w[MX],cnt[MX],p[MX],rk[MX],is[MX],s[MX],sit[MX];
vector<int> g[MX];
long long r;
void ofs(int i, int p, int mxs, bool fi=true) {
  //printf("ofs %d %d\n",i,p);
  for (int j=n; j>0; j&=j-1) if (sit[j]==it) r+=s[j];
  for (int j=mxs-i-1; j>0; j&=j-1) if (sit[j]==it) r-=s[j];
  //for (int j=1; j<=n; j++) if (is[j]) printf("%d,",j); puts("");
  for (int j=0; j<g[i].size(); j++) {
    int k=g[i][j];
    if (k==p || (fi && i+k>mxs)) continue;
    ofs(k,i,mxs,false);
  }
}
void ins(int i) {
  if (is[i]==it) return;
  is[i]=it;
  for (; i<=n; i=(i<<1)-(i&(i-1))) if (sit[i]!=it) { sit[i]=it; s[i]=1; } else s[i]++;
}
void dfs(int cur) {
  //printf("%d (%d %d) %d %d\n",cur,x[cur],y[cur],nx[cur],ny[cur]);
  if (nx[cur]!=0) {
    ++it;
    dfs(nx[cur]);
    ins(x[cur]);
  }
  if (ny[cur]!=0) {
    ++it;
    dfs(ny[cur]);
  }
  ins(y[cur]);
  //puts("--");
  ofs(x[cur],y[cur],x[cur]+y[cur]);
  ins(x[cur]);
}
bool cmp(int i, int j) { return x[i]+y[i]<x[j]+y[j]; }
int fs(int x) {
  if (x!=p[x]) p[x]=fs(p[x]);
  return p[x];
}
int main() {
  scanf("%d",&n);
  for (i=1; i<n; i++) {
    scanf("%d%d",&x[i],&y[i]);
    g[x[i]].push_back(y[i]);
    g[y[i]].push_back(x[i]);
    k[i-1]=i;
  }
  if (n==1) { puts("0"); return 0; }
  for (i=1; i<=n; i++) p[i]=i;
  sort(k,k+n-1,cmp);
  ++it;
  for (i=0; i<n-1; i++) {
    cur=k[i];
    xc=fs(x[cur]);
    yc=fs(y[cur]);
    if (xc==yc) continue;
    if (rk[yc]>=rk[xc]) {
      p[xc]=now=yc;
      if (rk[yc]==rk[xc]) rk[yc]++;
    } else p[yc]=now=xc;
    if (cnt[w[yc]]>=cnt[w[xc]]) {
      nx[cur]=w[xc];
      ny[cur]=w[yc];
    } else {
      nx[cur]=w[yc];
      ny[cur]=w[xc];
      swap(x[cur],y[cur]);
    }
    cnt[cur]=cnt[w[xc]]+cnt[w[yc]]+1;
    w[now]=cur;
  }
  dfs(cur);
  printf("%lld\n",r);
  return 0;
}