#include <bits/stdc++.h>
using namespace std;
vector<pair<long long int, long long int> > ans;
void solve(vector<vector<long long int> > &graph, long long int i,
           long long int parent, vector<long long int> &visited) {
  for (long long int j = 0; j < graph[i].size(); j++) {
    if (!visited[graph[i][j]]) {
      ans.push_back(make_pair(i, graph[i][j]));
      visited[graph[i][j]] = 1;
      solve(graph, graph[i][j], i, visited);
    }
  }
}
int main() {
  long long int n, m;
  cin >> n >> m;
  ans.clear();
  vector<vector<long long int> > graph(n);
  vector<long long int> temp(n);
  for (long long int i = 0; i < m; i++) {
    long long int u, v;
    cin >> u >> v;
    u--;
    v--;
    graph[u].push_back(v);
    graph[v].push_back(u);
    temp[u]++;
    temp[v]++;
  }
  vector<long long int> visited(n);
  long long int mx_i = max_element(temp.begin(), temp.end()) - temp.begin();
  long long int mx = *max_element(temp.begin(), temp.end());
  visited[mx_i] = 1;
  vector<long long int> arr;
  for (long long int j = 0; j < graph[mx_i].size(); j++) {
    visited[graph[mx_i][j]] = 1;
    arr.push_back(graph[mx_i][j]);
    ans.push_back(make_pair(mx_i, graph[mx_i][j]));
  }
  for (long long int i = 0; i < arr.size(); i++) {
    solve(graph, arr[i], mx, visited);
  }
  for (long long int i = 0; i < ans.size(); i++) {
    cout << ans[i].first + 1 << " " << ans[i].second + 1 << endl;
  }
}
