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

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Scanner;


public class E {
    static class Node{
        int id;
        ArrayList<Node> adjacent;
        HashSet<Integer> branch;
        boolean visited = false;
        Node(int id){
            this.id = id;
            adjacent = new ArrayList<>();
            branch = new HashSet<>();
        }
    }
    static ArrayList<Node> leaves;
    static int minHeight = Integer.MAX_VALUE;
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        Node[] nodes = new Node[n+1];

        leaves = new ArrayList<>();
        for(int i=0;i<n-1;i++){
            int u = scanner.nextInt();
            int v =scanner.nextInt();
            if(nodes[u] == null){
                nodes[u] = new Node(u);
            }
            if(nodes[v] == null){
                nodes[v] = new Node(v);
            }
            nodes[u].adjacent.add(nodes[v]);
            nodes[v].adjacent.add(nodes[u]);
        }
//        dfs(nodes[1],0,null);

        Node  root=null;
Node root1 = null;
        for(int i=1;i<=n;i++){
            if(nodes[i].adjacent.size() > 2){
                root = nodes[i];
            }
 if(nodes[i].adjacent.size() == 1){
                root1 = nodes[i];
            }
        }
if(root == null) 
if(n%2==0)
  minHeight = n-2;
else minHeight = n/2;

        dfs(root);
        if(minHeight==Integer.MAX_VALUE){
            System.out.println(-1);
        }else{
            System.out.println(minHeight+1);
        }


    }
    static int dfs(Node root){
        if(root == null){
            return Integer.MAX_VALUE;
        }
        if(root.visited){
            return Integer.MAX_VALUE;
        }
        if(root.adjacent.size() ==1){
            return 0;
        }
        int min=-Integer.MAX_VALUE;
        root.visited = true;
        for(Node node: root.adjacent){
            if(!node.visited){
                int temp = 1+dfs(node);
                if(root.adjacent.size() == 2){
                    return temp;
                }

                if(root.branch.contains(temp)){
                    if(temp < min){
                        min = temp;
                    }
                    if(temp<minHeight){
                        minHeight = temp;
                    }
                }else{
                    root.branch.add(temp);
                }
            }

        }
            return min+1;

    }

}