#include <bits/stdc++.h>
using namespace std;
inline int qpow(int b, int e, int m = 998244353) {
  int a = 1;
  for (; e; e >>= 1, b = (long long)b * b % m)
    if (e & 1) a = (long long)a * b % m;
  return a;
}
long long ans = 0;
void dfs(long long i, long long p, vector<vector<long long>> &adj,
         vector<long long> &stsize) {
  if (adj[i].size() == 1 && adj[i][0] == p) {
    stsize[i] = 1;
    return;
  }
  for (long long j = 0; j < adj[i].size(); j++) {
    long long v = adj[i][j];
    if (v == p) continue;
    dfs(v, i, adj, stsize);
    stsize[i] += stsize[v];
  }
  stsize[i]++;
}
void solve() {
  long long n;
  cin >> n;
  vector<vector<long long>> adj(n + 1);
  for (int i = 1; i < n; i++) {
    long long u, v;
    cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  if (n % 2 == 1) {
    cout << -1 << endl;
    return;
  }
  vector<long long> stsize(n + 1);
  dfs(1, 0, adj, stsize);
  for (int i = 2; i <= n; i++)
    if (stsize[i] != 0 && stsize[i] % 2 == 0) ans++;
  cout << ans << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t;
  t = 1;
  while (t--) solve();
  return 0;
}
