#include<bits/stdc++.h>
using namespace std;
const int N = 5e3 + 1;

vector<short>G[N];
short deep[N], f[N][N];
int g[N][N];

long long ans = 0;
int n;

void dfs(int u, int fa){
    f[u][0] = 1;
    for(auto v : G[u]){
        if(v == fa) continue;
        deep[v] = deep[u] + 1;
        dfs(v, u);
        for(int i = 0;i <= n;i ++) ans += g[u][i] * (i == 0 ? 0 : f[v][i - 1]) + g[v][i + 1] * f[u][i];
		for(int i = 0;i <= n;i ++) g[u][i] += f[u][i] * (i == 0 ? 0 : f[v][i - 1]) + g[v][i + 1];
		for(int i = 1;i <= n;i ++) f[u][i] += f[v][i-1];
    }
}

void solve(){
    
    cin >> n;
    for(int i = 1; i < n; i++){
        int u, v;
        cin >> u >> v;
        G[u].push_back(v);
        G[v].push_back(u);
    }
    dfs(1, 0);
    cout << ans << '\n';
}

int main(){
    int t = 1;
    //cin >> t;
    while(t--){
        solve();
    }
    return 0;
}