n = int(input())
tree = {}
node_count_edges = {}
u, v = map(int, input().split())
tree[u] = [v]
tree[v] = [u]
root = u
for i in range(n - 2):
u, v = map(int, input().split())
if u not in tree: tree[u] = []
if v not in tree: tree[v] = []
tree[u].append(v)
tree[v].append(u)
curr_nodes = [root]
l = 0
r = 0
i = 0
node_side = {}
passed = set()
while len(curr_nodes) != 0:
new_curr_nodes = []
for node in curr_nodes:
if node in passed:
continue
passed.add(node)
new_curr_nodes.extend(tree[node])
if i % 2 == 0:
node_side[node] = 'left'
else:
node_side[node] = 'right'
if i % 2 == 0:
l += 1
else:
r += 1
i += 1
curr_nodes = new_curr_nodes
ans = 0
for node in tree:
if node_side[node] == 'left':
ans += r - len(tree[node])
else:
ans += l - len(tree[node])
print(ans // 2)/*亲爱的上帝，我求你给我力量来赢得这场战斗。*/
#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define vl vector<i64>
#define vi vector<int>
template<typename T> bool chkmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chkmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
constexpr int mxN = 2e5;
vector<vector<int>> A(mxN);
vector<bool> vis(mxN), color(mxN, 0);
void solve() {
int N;
cin >> N;
for(int i=0; i<N-1; i++) {
int u, v;
cin >> u >> v;
A[--u].push_back(--v);
A[v].push_back(u);
}
i64 ONE = 0;
function<void(int, int)> dfs = [&](int x, int col) {
vis[x] = 1;
color[x] = col;
if(color[x]) ONE++;
for(int j:A[x]) {
if(!vis[j]) {
dfs(j, col ^ 1);
}
}
};
for(int i=0; i<N; i++) {
if(!vis[i]) {
dfs(i, 1);
}
}
cout << ONE *1LL* (N - ONE) - N + 1;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int TT=1;
// cin >> TT;
while(TT--){
solve();
}
}118A - String Task | 236A - Boy or Girl |
271A - Beautiful Year | 520B - Two Buttons |
231A - Team | 479C - Exams |
1030A - In Search of an Easy Problem | 158A - Next Round |
71A - Way Too Long Words | 160A - Twins |
1A - Theatre Square | 1614B - Divan and a New Project |
791A - Bear and Big Brother | 1452A - Robot Program |
344A - Magnets | 96A - Football |
702B - Powers of Two | 1036A - Function Height |
443A - Anton and Letters | 1478B - Nezzar and Lucky Number |
228A - Is your horseshoe on the other hoof | 122A - Lucky Division |
1611C - Polycarp Recovers the Permutation | 432A - Choosing Teams |
758A - Holiday Of Equality | 1650C - Weight of the System of Nested Segments |
1097A - Gennady and a Card Game | 248A - Cupboards |
1641A - Great Sequence | 1537A - Arithmetic Array |