10
4 2
7 4
2 6
2 5
4 8
10 3
2 9
9 1
5 10
 10
5 10
7 8
8 3
2 6
3 2
9 7
4 5
10 1
6 4
 4
4 1
4 3
4 2
 3
3 1
1 2
 9
1 2
1 3
1 4
1 5
1 6
6 7
6 8
8 9
 5
1 5
2 3
2 4
1 2
 8
6 1
4 7
4 8
8 5
7 6
4 3
4 2
 7
5 6
5 7
5 1
7 4
6 3
3 2
 3
1 3
3 2
 2
1 2
 5
5 4
4 3
3 1
5 2
 6
1 6
3 1
6 4
5 3
2 5
 11
8 9
2 7
1 11
3 2
9 1
8 5
8 6
5 4
4 10
8 3
 11
11 9
6 7
7 1
8 11
5 6
3 5
9 3
10 8
2 4
4 10
 12
12 6
6 7
8 11
4 8
10 4
12 3
2 10
6 2
12 9
4 1
9 5

-1
 9
 1
 1
 3
 3
 -1
 -1
 1
 1
 1
 5
 1
 5
 -1

#include <bits/stdc++.h>
using namespace std;
const int N = 200010;
int n, d[N], vis[N];
vector<int> G[N];
map<int, int> mp[N];
void merge(map<int, int> &a, map<int, int> &b) {
  for (auto i : a) {
    b[i.first + 1] += i.second;
    if (b[i.first + 1] % 2 == 0) {
      b.erase(i.first + 1);
    }
  }
  a.clear();
}
int main() {
  ios::sync_with_stdio(0);
  cin >> n;
  if (n == 2) return cout << 1, 0;
  for (int u, v, i = 1; i < n; i++) {
    cin >> u >> v;
    G[u].push_back(v);
    G[v].push_back(u);
    d[u]++, d[v]++;
  }
  queue<int> q;
  for (int i = 1; i <= n; i++) {
    if (d[i] == 1) {
      q.push(i);
      mp[i][0] = 1;
    }
  }
  while (q.size()) {
    int t = q.front();
    q.pop();
    if (vis[t]) continue;
    vis[t] = 1;
    for (auto i : G[t]) {
      d[i]--;
      if (d[i] >= 1) {
        merge(mp[t], mp[i]);
        if (d[i] == 1) {
          q.push(i);
        }
      }
    }
  }
  int ans = -1;
  for (int i = 1; i <= n; i++) {
    if (mp[i].size() == 1) {
      ans = 0;
      for (auto j : mp[i]) ans += j.first;
    } else if (mp[i].size() == 2) {
      ans = 0;
      for (auto j : mp[i]) ans += j.first;
    }
  }
  while (ans % 2 == 0) ans >>= 1;
  cout << ans;
}
