#include<cstdio>

#include<cstdlib>

#include<set>

#include<vector>

#include<iostream>

#define LL long long

#define int long long

using namespace std;

const int MAXN = 1e5 + 10;

inline int read() {

    char c = getchar(); int x = 0, f = 1;

    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}

    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();

    return x * f;

}

int N, siz[MAXN], son[MAXN], dsu[MAXN], Son, vis[MAXN], ds[MAXN];

vector<int> v[MAXN];

set<int> s;

LL outt, inn, ans;

void dfs(int x, int _fa)

{

    siz[x] = 1;

    for(int i = 0; i < v[x].size(); i++) {

        int to = v[x][i]; if(to == _fa) continue;

        dfs(to, x);

        siz[x] += siz[to];

        if(siz[to] > siz[son[x]]) son[x] = to;

    }

}

LL calc(LL x) {

    return x * (x - 1) / 2;

}

void Clear() {

    s.clear();

	outt = calc(N);

	inn = 0;

    s.insert(0);

	s.insert(N + 1);

}

int find(int x)

{

    return dsu[x] == x ? dsu[x] : dsu[x] = find(dsu[x]);

}

void solve(int x)

{

    s.insert(x);

    set<int>::iterator s1, s2, it;

    s1 = s2 = it = s.find(x);

    s1--; s2++;

    outt -= calc((*s2) - (*s1) - 1);

    outt += calc((*s2) - (*it) - 1) + calc((*it) - (*s1) - 1);

    vis[x] = 1;

    if(vis[x - 1]) {

        int fx = find(x - 1), fy = find(x);

        inn += ds[fx] * ds[fy];

        dsu[fx] = fy;

        ds[fy] += ds[fx];

    }

    if(vis[x + 1]) {

        int fx = find(x + 1), fy = find(x);

        inn += ds[fx] * ds[fy];

        dsu[fx] = fy;

        ds[fy] += ds[fx];

    }

}

void Add(int x, int fa)

{

    solve(x);

    for(int i = 0; i < v[x].size(); i++)

	{

        int to = v[x][i];

        if(to == fa || to == Son) continue;

        Add(to, x);

    }

}

void Delet(int x, int fa) {

    vis[x] = 0; ds[x] = 1; dsu[x] = x;

    for(int i = 0; i < v[x].size(); i++) {

        int to = v[x][i];

        if(to == fa) continue;

        Delet(to, x);

    }

}

void dfs2(int x, int fa, int opt)

{

    for(int i = 0; i < v[x].size(); i++)

	{

        int to = v[x][i];

       if(to == fa || (to == son[x])) continue;

        dfs2(to, x, 0);

    }

    if(son[x]) dfs2(son[x], x, 1); Son = son[x];

    Add(x, fa);

    ans += calc(N) - inn - outt;

    if(opt == 0) Delet(x, fa), Clear(), Son = 0;

}

signed main()

{

	#ifdef yilnr

	#else

	freopen("treecnt.in","r",stdin);

	freopen("treecnt.out","w",stdout);

	#endif

    N = read();

    for(int i = 1; i <= N - 1; i++)

	{

        int x = read(), y = read();

        v[x].push_back(y);

		v[y].push_back(x);

    }

    for(int i = 1; i <= N; i++) dsu[i] = i,ds[i] = 1;

	dfs(1,0);

    Clear();

    dfs2(1,0,0);

    printf("%lld\n",ans);

    return 0;

}

/*

4

1 4

1 3

2 4

*/