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;
inline void setmin(int &x, int y) {
  if (y < x) x = y;
}
inline void setmax(int &x, int y) {
  if (y > x) x = y;
}
inline void setmin(long long &x, long long y) {
  if (y < x) x = y;
}
inline void setmax(long long &x, long long y) {
  if (y > x) x = y;
}
const int N = 200000;
const int inf = (int)1e9 + 1;
const long long big = (long long)1e18 + 1;
const int P = 239;
const int MOD = (int)1e9 + 7;
const int MOD1 = (int)1e9 + 9;
const double eps = 1e-9;
const double pi = atan2(0, -1);
const int ABC = 26;
vector<int> g[N];
int dp[N], dp1[N];
void dfs(int u, int p) {
  set<int> val;
  for (int v : g[u])
    if (v != p) {
      dfs(v, u);
      val.insert(dp[v]);
    }
  if ((int)val.size() == 0)
    dp[u] = 1;
  else if ((int)val.size() == 1 && (*val.begin()) != -1)
    dp[u] = (*val.begin()) + 1;
  else
    dp[u] = -1;
}
void dfs1(int u, int p, int up) {
  map<int, int> val;
  for (int v : g[u])
    if (v != p) val[dp[v]]++;
  if (up != 0) val[up]++;
  if ((int)val.size() == 0)
    dp1[u] = 1;
  else if ((int)val.size() == 1 && val.begin()->first != -1)
    dp1[u] = val.begin()->first + 1;
  else if ((int)val.size() == 2 && val.begin()->first != -1)
    dp1[u] = val.begin()->first + (++val.begin())->first + 1;
  else
    dp1[u] = -1;
  for (int v : g[u])
    if (v != p) {
      val[dp[v]]--;
      if (val[dp[v]] == 0) val.erase(dp[v]);
      if ((int)val.size() == 0)
        dfs1(v, u, 1);
      else if ((int)val.size() == 1 && val.begin()->first != -1)
        dfs1(v, u, val.begin()->first + 1);
      else
        dfs1(v, u, -1);
      val[dp[v]]++;
    }
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.precision(20);
  cout << fixed;
  int n;
  cin >> n;
  for (int i = 0; i < n - 1; i++) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  dfs(0, -1);
  dfs1(0, -1, 0);
  int ans = -1;
  for (int i = 0; i < n; i++)
    if (dp1[i] != -1) {
      int x = dp1[i] - 1;
      while (x > 0 && x % 2 == 0) x /= 2;
      if (ans == -1 || x < ans) ans = x;
    }
  cout << ans << "\n";
  return 0;
}
