#include <bits/stdc++.h>
using namespace std;
const int N = 200000;
map<int, int> m[N];
set<int> nei[N];
int n, forks, a, b;
int rise(int v, int pv = -1, int d = 0) {
  if (nei[v].size() > 2)
    if (m[v].count(d))
      return nei[v].erase(m[v][d]), m[v].erase(d), forks -= nei[v].size() <= 2,
             1;
    else
      return m[v].insert({d, pv}), 0;
  for (auto i : nei[v])
    if (i != pv) return rise(i, v, d + 1);
  return d;
}
int main() {
  cin.tie(0), ios::sync_with_stdio(0);
  cin >> n;
  for (int i = 1; i < n; ++i)
    cin >> a >> b, nei[--a].insert(--b), nei[b].insert(a);
  for (int i = 0; i < n; ++i) forks += nei[i].size() > 2;
  for (int i = 0; i < n; ++i)
    if (nei[i].size() == 1)
      while (1)
        if (forks)
          if (!rise(i))
            break;
          else
            ;
        else
          return n = rise(i), cout << (n >> __builtin_ctz(n)), 0;
  cout << -1;
  return 0;
}
