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 int read() {
  int tot = 1;
  char c = getchar();
  while (c != '-' && (c < '0' || c > '9')) c = getchar();
  if (c == '-') c = getchar(), tot = -1;
  int sum = 0;
  while (c >= '0' && c <= '9') sum = sum * 10 + c - '0', c = getchar();
  return sum * tot;
}
const int N = 4 * 100005;
int root, pos, nxt[N], head[N], v[N];
void add(int u, int y) {
  nxt[++pos] = head[u];
  v[pos] = y;
  head[u] = pos;
}
int dfs(int u, int fa) {
  set<int> s;
  for (int i = head[u]; i; i = nxt[i]) {
    int j = v[i];
    if (j == fa) continue;
    int tmp = dfs(j, u);
    if (tmp == -1) return -1;
    s.insert(tmp + 1);
  }
  if (s.size() == 0) return 0;
  if (s.size() == 1) return *s.begin();
  if (s.size() == 2 && u == root) return *s.begin() + *s.rbegin();
  root = u;
  return -1;
}
int main() {
  int n = read();
  for (int i = 1; i < n; i++) {
    int x = read(), y = read();
    add(x, y);
    add(y, x);
  }
  int ans = dfs(1, 0);
  if (ans == -1) ans = dfs(root, 0);
  while (!(ans & 1)) ans >>= 1;
  cout << ans << endl;
}
