#include<bits/stdc++.h>

using namespace std;

#define inf 0x3f3f3f3f

#define ll long long

const int N=200005;

const int mod=1e9+7;

const double eps=1e-8;

const double PI = acos(-1.0);

#define lowbit(x) (x&(-x))

vector<int> g[N];

ll col[N],num[2];

void dfs(int u,int fa)

{

    for(int v:g[u])

    {

        if(v==fa)

            continue;

        col[v]=col[u]^1;

        num[col[v]]++;

        dfs(v,u);

    }

}

int main()

{

    std::ios::sync_with_stdio(false);

    int n;

    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);

    }

    num[0]++;

    col[1]=0;

    dfs(1,0);

    cout<<num[0]*num[1]-(n-1)<<endl;

    return 0;

}