#include <bits/stdc++.h>
using namespace std;
void speedup() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
long long expo(long long a, long long b, long long m) {
  long long res = 1;
  while (b) {
    if (b % 2 == 1) res = (res * a) % m;
    a = (a * a) % m;
    b /= 2;
  }
  return res;
}
long long ans = 0;
vector<long long> v[100001];
int dfs(long long parent, long long node) {
  long long i, s = 1;
  for (auto k : v[node]) {
    if (k != parent) s += dfs(node, k);
  }
  if (s % 2 == 0 && parent != -1) ans++;
  return s;
}
int main() {
  speedup();
  long long n;
  cin >> n;
  long long a, b, i;
  for (i = 0; i <= n - 2; i++) {
    cin >> a >> b;
    v[a].push_back(b);
    v[b].push_back(a);
  }
  if (n % 2 == 0) {
    dfs(-1, a);
    cout << ans;
  } else
    cout << "-1";
  return 0;
}
