#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 7;
int n, G[N], _[N], dp[N];
queue<int> h;
vector<int> adj[N];
int root = -1;
void aedge(int u, int v) {
  adj[u].push_back(v);
  adj[v].push_back(u);
}
int ans = 0;
void disconnect(int u) {
  for (int v : adj[u])
    if (G[v] > 1 || v == root) {
      ++ans;
      --G[v];
      if (G[v] == 1) h.push(v);
    }
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i < n; ++i) {
    int u, v;
    scanf("%d %d", &u, &v);
    aedge(u, v);
    ++G[u];
    ++G[v];
    ++_[u];
    ++_[v];
  }
  for (int i = 1; i <= n; ++i)
    if (_[i] == 1) h.emplace(i);
  while (!h.empty()) {
    int u = h.front();
    h.pop();
    root = u;
    for (int v : adj[u])
      if (_[v] > 1) {
        _[v]--;
        if (_[v] == 1) h.push(v);
      }
  }
  for (int i = 1; i <= n; ++i) {
    if (G[i] == 1) h.emplace(i);
    dp[i] = 1;
  }
  while (!h.empty()) {
    int u = h.front();
    h.pop();
    if ((dp[u] & 1) == 0)
      disconnect(u);
    else {
      for (int v : adj[u]) {
        if (G[v] > 1 || root) {
          --G[v];
          dp[v] += dp[u];
          if (G[v] == 1) h.push(v);
        }
      }
    }
  }
  if (n & 1)
    printf("-1\n");
  else
    printf("%d\n", ans);
  return 0;
}
