import java.util.*;

public class Solution {

    static Scanner sc = new Scanner(System.in);


    public static ArrayList<Integer> athleticRace(int N,int M,ArrayList<Integer>[] A){
    	ArrayList<Integer> result = new ArrayList<>();

    	int[] time = new int[M+1];

    	for(int i=1;i<=M;i++) {
    		time[i] = -1;
    	}

    	Queue<Integer> q = new LinkedList<>();
    	q.add(M);
    	time[M] = 0;

    	while(!q.isEmpty()) {
    		int temp = q.remove();

    		for(int i : A[temp]) {
    			if(time[i] == -1) {
    				time[i] = time[temp]+1;
    				q.add(i);
    			}
    		}
    	}

    	int max_time = 0;
    	HashSet<Integer> hs = new HashSet<>();

    	for(int i=1;i<=N;i++) {
    		hs.add(time[i]);
    		if(max_time < time[i]) {
    			max_time = time[i];
    		}
    	}

    	if(hs.size() == 1) {
    		result.add(-1);
    		return result;
    	}

    	for(int i=1;i<=N;i++) {
    		if(max_time == time[i]) {
    			result.add(i);
    		}
    	}

    	return result;
    }

    public static void main(String[] args) {
    	int N,M;
        N = sc.nextInt();
        M = sc.nextInt();

        ArrayList<Integer>[] A = new ArrayList[M+1];
        for(int i=0;i<=M;i++) {
        	A[i] = new ArrayList<>();
        }

        for(int i = 0;i<M-1;i++) {
        	int temp1 = sc.nextInt();
        	int temp2 = sc.nextInt();

        	A[temp1].add(temp2);
        	A[temp2].add(temp1);
        }

        ArrayList<Integer> result = athleticRace(N,M,A);

        for(int i : result) {
        	System.out.print(i + " ");
        }
        System.out.println();
    }
}