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;
vector<vector<int> > e;
int r = -1;
int dfs(int i, int p, bool F) {
  vector<int> R;
  for (int x = 0; x < e[i].size(); x++) {
    int j = e[i][x];
    if (j == p) continue;
    int k = dfs(j, i, F);
    if (k == -1) {
      return -1;
    }
    R.push_back(k + 1);
  }
  int K = R.size();
  if (K == 0) {
    return 0;
  }
  bool G = 0;
  for (int x = 1; x < K; x++) {
    if (R[0] != R[x]) {
      G = 1;
    }
  }
  if (G) {
    if (!F) {
      r = i;
    }
    return -1;
  }
  return R[0];
}
int main() {
  int n;
  scanf("%d", &n);
  e = vector<vector<int> >(n);
  for (int i = 0; i < n - 1; i++) {
    int a, b;
    scanf("%d%d", &a, &b);
    a--, b--;
    e[a].push_back(b);
    e[b].push_back(a);
  }
  r = -1;
  int ret = dfs(0, -1, 0);
  if (ret == -1) {
    vector<int> V;
    bool F = 0;
    for (int x = 0; x < e[r].size(); x++) {
      int j = e[r][x];
      int k = dfs(j, r, 1);
      if (k == -1) {
        F = 1;
        break;
      }
      V.push_back(k + 1);
    }
    if (!F) {
      sort(V.begin(), V.end());
      int K = V.size();
      for (int i = 0; i < K; i++) {
        if (V[i] != V[0] && V[i] != V[K - 1]) {
          F = 1;
        }
      }
      if (!F) {
        ret = V[0] + V[K - 1];
      }
    }
  }
  while (ret % 2 == 0) {
    ret /= 2;
  }
  printf("%d\n", ret);
  return 0;
}
