OstovvTrEE

import java.util.*;
import java.lang.Math;
public class Uyi {
    static Scanner s = new Scanner(System.in);
    static int n = s.nextInt();
    static int m = s.nextInt();
    static ArrayList<Integer> [] a = new ArrayList[n];
    static ArrayList<Integer>[] tree = new ArrayList[n];
    static int [] used = new int [n];
    public static void main(String[] args) {
        for (int i = 0; i < n; i++) {
            a[i] = new ArrayList<>();
            tree[i] = new ArrayList<>();
        }
        for (int i = 0; i < m; i++) {
            int f = s.nextInt()-1;
            int se = s.nextInt()-1;
            a[se].add(f);
            a[f].add(se);
        }
        bfs(0);
        int [] used = new int [n];
        for (int i = 0; i < n; i++){
            used[i] = 1;
            for (int v2: tree[i]) {
                if (used[v2] == 0)
                System.out.println((i+1) + " " + (v2 + 1));
            }
        }
    }
    static void bfs(int start){
        Q q = new Q(100000);
        q.push(start);
        used[start] = 1;
        while (q.tail - q.head != 0){
            int v = q.pop();
            for (int v2 : a[v]) {
                if (used[v2] == 0){
                    used[v2] = 1;
                    q.push(v2);
                    tree[v].add(v2);
                    tree[v2].add(v);
                }
            }
        }
    }
}
class Q{
    int [] a;
    int head = 0;
    int tail = 0;
    Q(int n){
        a = new int [n];
    }
    int pick(){
        return a[head];
    }
    int pop(){
        return a[head++];
    }
    void push(int k){
        a[tail++] = k;
    }
}