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;
set<int> edge[200005];
set<int> path[200005];
int deg[200005];
queue<int> que;
int main() {
  int n;
  scanf("%d", &n);
  memset(deg, 0, sizeof(deg));
  for (int i = 1; i < n; i++) {
    int u, v;
    scanf("%d %d", &u, &v);
    edge[u].insert(v);
    edge[v].insert(u);
    deg[u]++;
    deg[v]++;
  }
  for (int i = 1; i <= n; i++) {
    if (deg[i] == 1) {
      que.push(i);
    }
  }
  int ans = -1;
  while (!que.empty()) {
    int wh = que.front();
    que.pop();
    if (path[wh].size() == 0) {
      edge[*edge[wh].begin()].erase(wh);
      path[*edge[wh].begin()].insert(1);
      if (edge[*edge[wh].begin()].size() == 1)
        que.push(*edge[wh].begin());
      else if (edge[*edge[wh].begin()].size() == 0) {
        wh = *edge[wh].begin();
        if (path[wh].size() == 1) {
          ans = *path[wh].begin();
          while (!(ans & 1)) ans >>= 1;
        } else if (path[wh].size() == 2) {
          ans = 0;
          for (set<int>::iterator it = path[wh].begin(); it != path[wh].end();
               it++)
            ans += *it;
          while (!(ans & 1)) ans >>= 1;
        }
        break;
      }
    } else if (path[wh].size() == 1) {
      edge[*edge[wh].begin()].erase(wh);
      path[*edge[wh].begin()].insert(*path[wh].begin() + 1);
      if (edge[*edge[wh].begin()].size() == 1)
        que.push(*edge[wh].begin());
      else if (edge[*edge[wh].begin()].size() == 0) {
        wh = *edge[wh].begin();
        if (path[wh].size() == 1) {
          ans = *path[wh].begin();
          while (!(ans & 1)) ans >>= 1;
        } else if (path[wh].size() == 2) {
          ans = 0;
          for (set<int>::iterator it = path[wh].begin(); it != path[wh].end();
               it++)
            ans += *it;
          while (!(ans & 1)) ans >>= 1;
        }
        break;
      }
    }
  }
  printf("%d\n", ans);
  return 0;
}
