#include <bits/stdc++.h>
using namespace std;
int dirx[] = {1, 0, -1, 0};
int diry[] = {0, 1, 0, -1};
int a;
vector<int> graph[100005];
int dist[100005];
bool visit[100005];
int cnt = 0;
bool flag = false;
int dfs(int u, int par) {
  visit[u] = true;
  for (int i = 0; i < graph[u].size(); i++) {
    if (!visit[graph[u][i]]) dist[u] += dfs(graph[u][i], u);
  }
  if (dist[u] != 0 && (dist[u] + 1) % 2 == 0) {
    cnt++;
    dist[u] = 0;
    return 0;
  } else
    return 1;
}
int main() {
  scanf("%d", &a);
  int x, y;
  int start = 0;
  for (int i = 0; i < a - 1; i++) {
    scanf("%d %d", &x, &y);
    start = x;
    graph[x].push_back(y);
    graph[y].push_back(x);
  }
  if (a % 2 == 1) {
    cout << -1 << endl;
    return 0;
  }
  dfs(start, 0);
  cout << cnt - 1 << endl;
}
