#include<bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(int i=(a),i##end=(b);i<=i##end;++i)
#define per(i,a,b) for(int i=(a),i##end=(b);i>=i##end;--i)
mt19937 Rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
template<typename T>void chkmax(T&x,T y){if(x<y)x=y;}
template<typename T>void chkmin(T&x,T y){if(x>y)x=y;}

#define pb push_back
#define ALL(x) (x).begin(),(x).end()
#define mem(x) memset((x),0,sizeof(x))

typedef double db;
typedef long long ll;
typedef vector<int>vi;
typedef pair<int,int>pii;

typedef unsigned u32;
typedef unsigned uint;
typedef unsigned long long u64;

namespace orzjk{
  const int SZ=1e6;
  char buf[SZ],*p1=buf,*p2=buf;
  char nc(){
    return p1==p2&&(p2=(p1=buf)+fread(buf,1,SZ,stdin),p1==p2)?EOF:*p1++;
  }
  char fub[SZ],*p3=fub,*p4=fub+SZ;
  void pc(char c){
    p3==p4&&(fwrite(fub,1,SZ,stdout),p3=fub);
    *p3++=c;
  }
  void flush(){
    fwrite(fub,1,p3-fub,stdout),p3=fub;
  }
}
using orzjk::nc;
using orzjk::pc;

//#define nc getchar
//#define pc putchar

int read(){
  int x=0,f=1;char c=nc();
  while(c<48)c=='-'&&(f=-1),c=nc();
  while(c>47)x=x*10+(c^48),c=nc();
  return x*f;
}
void write(int x){
  static char st[21];
  if(!x)return pc(48),void();
  char*p=st;
  if(x<0)x=-x,pc('-');
  for(;x;x/=10)*p++=x%10|48;
  do{
    pc(*--p);
  }while(p!=st);
}

//const int P=1e9+7;
const int P=998244353;
int qp(int a,int k){
  int res=1;for(;k;k>>=1,a=1ll*a*a%P)if(k&1)res=1ll*res*a%P;return res;
}

const int maxn=1e5+10;
int n;uint ans;u64 dt;

namespace T2{

struct edge{
  int u,v;
}G[maxn];

vi E[maxn];int deg[maxn];

int lg[maxn];
pii st[17][maxn];
int dep[maxn],dfn[maxn],seq[maxn];
u64 sz[maxn],F1[maxn],F2[maxn],G1[maxn],G2[maxn];
void dfs1(int u,int f){
  static int now;
  st[0][now]={dfn[f],f},dfn[u]=++now,seq[now]=u;
  sz[u]=1,dep[u]=dep[f]+1;
  for(int v:E[u])if(v!=f){
    dfs1(v,u),sz[u]+=sz[v];
    F1[u]+=F1[v]+sz[v];
    F2[u]+=F2[v]+2*F1[v]+sz[v];
  }
}
void dfs2(int u,int f){
//  printf("(%u %u) (%u %u)\n",F1[u],F2[u],G1[u],G2[u]);
  dt+=G2[u];
  for(int v:E[u])if(v!=f){
    G1[v]=G1[u]-sz[v]+(n-sz[v]);
    G2[v]=G2[u]-2*F1[v]-sz[v]+2*(G1[u]-F1[v]-sz[v])+n-sz[v];
    dfs2(v,u);
  }
}
int qlca(int u,int v){
  if(u==v)return u;
  u=dfn[u],v=dfn[v];
  if(u>v)swap(u,v);
  int k=lg[v-u];pii*seq=st[k];
  return min(seq[u],seq[v-(1<<k)]).second;
}
int qdis(int u,int v){
  return dep[u]+dep[v]-2*dep[qlca(u,v)];
}

void init(){
  rep(i,1,n-1){
    int u=read(),v=read();
    G[i]={u,v},deg[u]++,deg[v]++;
  }
  rep(i,1,n)E[i].reserve(deg[i]);
  rep(i,1,n-1){
    int u=G[i].u,v=G[i].v;
    E[u].pb(v),E[v].pb(u);
  }
  dfs1(1,0);
  G1[1]=F1[1],G2[1]=F2[1];
  dfs2(1,0);
//  rep(i,1,n)printf("%d%c",dfn[i],"\n "[i<iend]);
//  rep(i,1,n)printf("(%d %d)%c",st[0][i].first,st[0][i].second,"\n "[i<n]);
  rep(i,2,n)lg[i]=lg[i>>1]+1;
  rep(i,1,16)rep(j,1,n-(1<<i))st[i][j]=min(st[i-1][j],st[i-1][j+(1<<(i-1))]);
}

}

namespace virT{

int sumsz;
int clo,tim[maxn];
uint coef,D[maxn];

int ecnt,h[maxn];
struct edge{
  int nxt,to,w;
}E[maxn];
void addline(int u,int v){
  using T2::dep;
//  printf("(%d %d)\n",u,v);
  E[++ecnt]={h[u],v,dep[v]-dep[u]},h[u]=ecnt;
}

uint sz[maxn],F[maxn],G[maxn];
void dfs1(int u){
  F[u]=0,sz[u]=tim[u]==clo;
  for(int i=h[u];i;i=E[i].nxt){
    int v=E[i].to;
    dfs1(v),sz[u]+=sz[v],F[u]+=F[v]+E[i].w*sz[v];
  }
//  printf("!%d, %d\n",u,F[u]);
}

void dfs2(int u){
  for(int i=h[u];i;i=E[i].nxt){
    int v=E[i].to;
    G[v]=G[u]+E[i].w*(sumsz-2*sz[v]);
    dfs2(v);
  }
}

void calc(const vi&V,uint coef){
  if(V.size()<10u){
    for(int x:V){
      u32 s=0;
      for(int y:V)s+=T2::qdis(x,y);
      ans+=2*coef*D[x]*s;
    }
    return;
  }
//  puts("GG");
  virT::coef=coef;
  using T2::dfn;
  using T2::qlca;
  static int st[maxn];
  int top=0;ecnt=0;
  sumsz=V.size(),clo++;
  for(int u:V){
//    printf("[%d]\n",u);
    h[u]=0,tim[u]=clo;
    if(!top){
      st[++top]=u;continue;
    }
    int anc=qlca(st[top],u);
    if(anc!=st[top]){
      while(top>1&&dfn[anc]<dfn[st[top-1]]){
        addline(st[top-1],st[top]),top--;
      }
      if(top>1&&st[top-1]==anc){
        addline(anc,st[top--]);
      }else{
        h[anc]=0,addline(anc,st[top]),st[top]=anc;
      }
    }
    st[++top]=u;
  }
  rep(i,1,top-1)addline(st[i],st[i+1]);
  dfs1(st[1]);
  G[st[1]]=F[st[1]];
  dfs2(st[1]);
  for(int u:V)ans+=2*coef*D[u]*G[u];
//  for(int u:V)printf("(%d), %d %d\n",u,D[u],G[u]);
//  puts("gg");
}

}

namespace T1{

using virT::D;

struct edge{
  int u,v;
}G[maxn];

vi E[maxn];int deg[maxn];

u64 sz[maxn],F1[maxn],F2[maxn],G1[maxn],G2[maxn];
void dfs1(int u,int f){
  sz[u]=1;
  for(int v:E[u])if(v!=f){
    dfs1(v,u),sz[u]+=sz[v];
    F1[u]+=F1[v]+sz[v];
    F2[u]+=F2[v]+2*F1[v]+sz[v];
  }
}
void dfs2(int u,int f){
  dt+=G2[u];
  for(int v:E[u])if(v!=f){
    G1[v]=G1[u]-sz[v]+(n-sz[v]);
    G2[v]=G2[u]-2*F1[v]-sz[v]+2*(G1[u]-F1[v]-sz[v])+n-sz[v];
    dfs2(v,u);
  }
}

bool vis[maxn];
uint sck,sumsz;
void dfs3(int u,int f){
  sumsz++,sz[u]=1;
  for(int v:E[u])if(v!=f&&!vis[v]){
    dfs3(v,u),sz[u]+=sz[v];
  }
}
void dfs4(int u,int f){
  u64 s=sumsz-sz[u];
  for(int v:E[u])if(v!=f&&!vis[v]){
    dfs4(v,u),chkmax(s,sz[v]);
  }
  if(s*2<=sumsz)sck=u;
}
void dfs5(int u,int f){
  D[u]=D[f]+1;
  for(int v:E[u])if(v!=f&&!vis[v]){
    dfs5(v,u);
  }
}
uint tmp[maxn];
void dfs6(int u,int f){
  tmp[u]=tmp[f]+1,D[u]-=tmp[u];
  for(int v:E[u])if(v!=f&&!vis[v]){
    dfs6(v,u);
  }
}
vi vec[maxn],son[maxn];
struct cmp{
  bool operator()(int x,int y){
    return vec[x].size()>vec[y].size();
  }
};
void divide(int rt,int f){
//  printf("!%d\n",rt);
  sumsz=0,dfs3(rt,0),dfs4(rt,0),rt=sck;
//  printf("#%d\n",rt);
  vis[rt]=1,D[rt]=tmp[rt]=0;
  if(f)son[f].push_back(rt);
  for(int v:E[rt])if(!vis[v]){
    divide(v,rt);
    dfs6(v,rt);
  }
  priority_queue<int,vi,cmp>Q;
  for(int v:son[rt]){
//    printf("[%d : %d]\n",rt,v);
    virT::calc(vec[v],1),Q.push(v);
  }
  vec[rt].push_back(rt);
  Q.push(rt);
  while(Q.size()>1u){
    int x=Q.top();Q.pop();
    int y=Q.top();Q.pop();
    vi&A=vec[x],&B=vec[y];
    int sx=A.size(),sy=B.size();
    vi ano(sx+sy);
    using T2::dfn;
    for(int p=0,p1=0,p2=0;p<sx+sy;p++){
      if(p2==sy||(p1<sx&&dfn[A[p1]]<dfn[B[p2]])){
        ano[p]=A[p1++];
      }else{
        ano[p]=B[p2++];
      }
    }
    vi tmp;
    if(y!=rt){
      A.swap(ano);
      B.swap(tmp);
      Q.push(x);
    }else{
      B.swap(ano);
      A.swap(tmp);
      Q.push(y);
    }
  }
  sumsz=0,dfs3(rt,0);//assert(sumsz==vec[rt].size());
//  printf("@%d : ",rt);for(int x:vec[rt])printf("%d ",x);puts("");
  for(int v:vec[rt])D[v]=tmp[v];
  if(!f)virT::calc(vec[rt],1);
  vis[rt]=0;
}

void init(){
  rep(i,1,n-1){
    int u=read(),v=read();
    G[i]={u,v},deg[u]++,deg[v]++;
  }
  rep(i,1,n)E[i].reserve(deg[i]);
  rep(i,1,n-1){
    int u=G[i].u,v=G[i].v;
    E[u].pb(v),E[v].pb(u);
  }
  dfs1(1,0);
  G1[1]=F1[1],G2[1]=F2[1];
  dfs2(1,0);
}

}

void solve(){
  n=read();
  T1::init();
  T2::init();
  ans=dt/2;
  T1::divide(1,0);
  cout<<ans<<endl;
}

signed main(){
//  freopen("data.in","r",stdin);
//  freopen(".out","w",stdout);
//  int T;cin>>T;while(T--)solve();
  solve();
  orzjk::flush();
  return 0;
}