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 inf = 0x3f3f3f3f;
const int kMaxN = 2e5 + 5;
vector<int> vertex[kMaxN];
int parent[kMaxN];
bool visited[kMaxN];
void Root(int node) {
  visited[node] = true;
  for (int i = 0; i < (int)vertex[node].size(); i += 1) {
    int oth = vertex[node][i];
    if (visited[oth]) {
      vertex[node][i] = vertex[node].back();
      vertex[node].pop_back();
      i -= 1;
    } else {
      parent[oth] = node;
      Root(oth);
    }
  }
  visited[node] = false;
}
int path[kMaxN];
void ClearPaths(int node) {
  sort(vertex[node].begin(), vertex[node].end(),
       [&](int a, int b) { return path[a] < path[b]; });
  int last_path = 0;
  vector<int> remaining;
  for (int i = 0; i < (int)vertex[node].size(); i += 1) {
    int a = vertex[node][i];
    if (path[a] == last_path and last_path != 0) {
    } else {
      remaining.push_back(a);
      last_path = path[a];
    }
  }
  vertex[node] = remaining;
}
void ComputePaths(int node) {
  for (auto itr : vertex[node]) {
    ComputePaths(itr);
  }
  ClearPaths(node);
  if (vertex[node].size() == 0) {
    path[node] = 1;
    return;
  } else if (vertex[node].size() == 1) {
    if (path[vertex[node][0]]) {
      path[node] = 1 + path[vertex[node][0]];
    }
    return;
  } else {
    path[node] = 0;
  }
}
void Fail() {
  cout << "-1\n";
  exit(0);
}
void Answer(int val) {
  while (val > 0 and val % 2 == 0) {
    val /= 2;
  }
  cout << val << '\n';
  exit(0);
}
void GoRootDown(int node) {
  ClearPaths(node);
  int num_bad = 0;
  for (auto itr : vertex[node]) {
    num_bad += (path[itr] == 0);
  }
  if (num_bad > 1) {
    Answer(-1);
  } else if (num_bad == 0) {
    if (vertex[node].size() == 0) {
      Answer(0);
    }
    if (vertex[node].size() == 1) {
      Answer(path[vertex[node][0]]);
    }
    if (vertex[node].size() == 2) {
      Answer(path[vertex[node][0]] + path[vertex[node][1]]);
    }
    Answer(-1);
  }
  if (vertex[node].size() == 1) {
    path[node] = 1;
    vertex[vertex[node][0]].push_back(node);
    assert(path[vertex[node][0]] == 0);
    GoRootDown(vertex[node][0]);
  } else if (vertex[node].size() == 2) {
    path[node] = 1 + path[vertex[node][1]];
    vertex[vertex[node][0]].push_back(node);
    assert(path[vertex[node][0]] == 0);
    GoRootDown(vertex[node][0]);
  } else {
    Answer(-1);
  }
  assert(0);
}
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  for (int i = 0; i + 1 < n; i += 1) {
    int a, b;
    cin >> a >> b;
    vertex[a].push_back(b);
    vertex[b].push_back(a);
  }
  Root(1);
  ComputePaths(1);
  GoRootDown(1);
  return 0;
}
