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 = 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;
}
