#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<bitset>
#include<random>
#include<cmath>
#include<ctime>
#include<queue>
#include<map>
#include<set>

#define uint unsigned int
#define fi first
#define se second
#define max Max
#define min Min
#define abs Abs
#define lc (x<<1)
#define rc (x<<1|1)
#define mid ((l+r)>>1)
#define pb(x) push_back(x)
#define lowbit(x) ((x)&(-(x)))
#define fan(x) ((((x)-1)^1)+1)
#define mp(x,y) make_pair(x,y)
#define clr(f,n) memset(f,0,sizeof(int)*(n))
#define cpy(f,g,n) memcpy(f,g,sizeof(int)*(n))
#define SZ(x) ((int)(x.size()))
#define INF 0x3f3f3f3f

using namespace std;

inline int read()
{
	int ans=0,f=1;
	char c=getchar();
	while(c>'9'||c<'0'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9'){ans=(ans<<1)+(ans<<3)+c-'0';c=getchar();}
	return ans*f;
}

inline void write(uint x)
{
	if(x/10) write(x/10);
	putchar((char)(x%10)+'0');
}

template<typename T>inline T Abs(T a){return a>0?a:-a;};
template<typename T,typename TT>inline T Min(T a,TT b){return a<b?a:b;}
template<typename T,typename TT> inline T Max(T a,TT b){return a<b?b:a;}

const int N=2e5+5;
int n,vis[N],dep[N],a[N<<1],b[N],Cnt,St[20][N<<1],dfn[N],cnt;
uint ans;

struct Edge
{
	int v,w,ne;
}e[2][N];
int head[2][N],tot[2];

inline void add(int p,int u,int v,int w=0)
{
	e[p][++tot[p]]=(Edge){v,w,head[p][u]};
	head[p][u]=tot[p];
}

int mn,ps,sz[N],all;

void dfs0(int u,int fa)
{
	all++;
	for(int i=head[0][u];i;i=e[0][i].ne)
	{
		int v=e[0][i].v;
		if(v==fa||vis[v])
			continue;
		dfs0(v,u);
	}
}

void dfs1(int u,int fa)
{
	sz[u]=1;int tmp=0;
	for(int i=head[0][u];i;i=e[0][i].ne)
	{
		int v=e[0][i].v;
		if(v==fa||vis[v])
			continue;
		dfs1(v,u);sz[u]+=sz[v];
		tmp=max(tmp,sz[v]);
	}
	tmp=max(tmp,all-sz[u]);
	if(tmp<mn) mn=tmp,ps=u;
}

inline int findrt(int u)
{
	all=0;mn=INF;ps=-1;
	dfs0(u,0);dfs1(u,0);
	return ps;
}

void dfs(int u,int fa)
{
	dfn[u]=++cnt;
	dep[u]=dep[fa]+1;
	a[++Cnt]=u;b[u]=Cnt;
	for(int i=head[1][u];i;i=e[1][i].ne)
	{
		int v=e[1][i].v;
		if(v==fa) continue;
		dfs(v,u);
		a[++Cnt]=u;
	}
}

inline int LCA(int x,int y)
{
	x=b[x];y=b[y];
	if(x>y) swap(x,y);
	int k=__lg(y-x+1);
	if(dep[St[k][x]]<dep[St[k][y-(1<<k)+1]])
		return St[k][x];
	return St[k][y-(1<<k)+1];
}

vector<int> hv;
int val[N],st[N],top;

inline void insert(int x)
{
	int lst=st[top];top--;
	while(top&&LCA(st[top],x)!=st[top])
	{
		add(1,st[top],lst,dep[lst]-dep[st[top]]);
		lst=st[top];top--;
	}
	int lca=LCA(lst,x);
	if(lca!=lst)
	{
		add(1,lca,lst,dep[lst]-dep[lca]);
		hv.push_back(lca);
	}
	if(st[top]!=lca)
		st[++top]=lca;
	hv.push_back(x);
	st[++top]=x;
}

uint f0[N],f1[N],f2[N],res;

void DP(int u,int fa)
{
	if(val[u]!=-1)
	{
		f0[u]=1,f1[u]=val[u],f2[u]=val[u]*1u*val[u];
		res+=val[u]*1u*val[u];
	}
	else f0[u]=0,f1[u]=0,f2[u]=0;
	for(int i=head[1][u];i;i=e[1][i].ne)
	{
		int v=e[1][i].v;
		if(v==fa) continue;
		DP(v,u);
		uint F0=f0[v],F1=f1[v]+f0[v]*e[1][i].w;
		uint F2=f2[v]+2*f1[v]*e[1][i].w+f0[v]*e[1][i].w*e[1][i].w;
		res+=f0[u]*F2+2*f1[u]*F1+f2[u]*F0;
		f2[u]+=F2;f1[u]+=F1;f0[u]+=F0;
	}
}

inline uint query(vector<int> nd)
{
	st[++top]=1;hv.push_back(1);res=0;
	for(auto i:nd) if(i!=1) insert(i);
	for(int i=1;i<top;++i)
		add(1,st[i],st[i+1],dep[st[i+1]]-dep[st[i]]);
	DP(1,0);
	for(auto i:hv)
		head[1][i]=0,val[i]=-1;
	tot[1]=0;nd.clear();hv.clear();top=0;
	return res;
}

void dfs2(int u,int fa,int len)
{
	val[u]=len;
	for(int i=head[0][u];i;i=e[0][i].ne)
	{
		int v=e[0][i].v;
		if(v==fa||vis[v]) continue;
		dfs2(v,u,len+1);
	}
}

struct node
{
	int u,w;
	bool operator < (const node &x)const
	{
		return dfn[w]>dfn[x.w];
	}
};

int lim[N];

vector<int> solve(int u)
{
	u=findrt(u);vis[u]=1;
	vector<int> now;
	vector<vector<int> > merg;
	for(int i=head[0][u];i;i=e[0][i].ne)
	{
		int v=e[0][i].v;
		if(vis[v]) continue;
		vector<int> tmp=solve(v);
		dfs2(v,u,1);ans-=query(tmp);
		merg.push_back(tmp);
	}
	priority_queue<node> qu;
	for(int i=0;i<SZ(merg);++i)
		lim[i]=0,qu.push((node){i,merg[i][lim[i]++]});
	int flg=0;
	while(!qu.empty())
	{
		int U=qu.top().u;
		int w=qu.top().w;
		if(dfn[u]<dfn[w])
			now.push_back(u),flg=1;
		now.push_back(w);qu.pop();
		if(lim[U]<SZ(merg[U]))
			qu.push((node){U,merg[U][lim[U]++]});
	}
	if(!flg) now.push_back(u);
	vis[u]=0;
	dfs2(u,0,0);
	ans+=query(now);
	return now;
}

signed main()
{
	n=read();
	for(int i=1;i<n;++i)
	{
		int u=read(),v=read();
		add(0,u,v);add(0,v,u);
	}
	for(int i=1;i<n;++i)
	{
		int u=read(),v=read();
		add(1,u,v);add(1,v,u);
	}
	dfs(1,0);
	for(int i=1;i<=Cnt;++i)
		St[0][i]=a[i];
	for(int j=1;j<20;++j)
		for(int i=1;i+(1<<j)-1<=Cnt;++i)
			if(dep[St[j-1][i]]<dep[St[j-1][i+(1<<(j-1))]])
				St[j][i]=St[j-1][i];
			else St[j][i]=St[j-1][i+(1<<(j-1))];
	for(int i=1;i<=n;++i)
		head[1][i]=0;tot[1]=0;
	memset(val,-1,sizeof(val));
	solve(1);
	write(ans);
	return 0;
}