#include <bits/stdc++.h>
using namespace std;
vector<long long> graph[200010];
long long v[200010], new_visit[200010], MAX_node, mx, cnt;
void dfs(long long node) {
  v[node] = 1;
  if ((long long)graph[node].size() > mx) {
    mx = (long long)graph[node].size();
    MAX_node = node;
  }
  for (auto &x : graph[node])
    if (!v[x]) dfs(x);
}
void bfs(long long node) {
  queue<long long> q;
  q.push(node);
  while (!q.empty()) {
    long long frt = q.front();
    new_visit[frt] = 1;
    q.pop();
    for (auto &x : graph[frt]) {
      if (!new_visit[x]) {
        new_visit[x] = 1;
        cout << frt << " " << x << endl;
        q.push(x);
        cnt--;
        if (cnt == 0) return;
      }
    }
  }
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, m;
  cin >> n >> m;
  cnt = n - 1;
  for (long long i = 0; i < m; i++) {
    long long x, y;
    cin >> x >> y;
    graph[x].push_back(y);
    graph[y].push_back(x);
  }
  dfs(1);
  bfs(MAX_node);
}
