#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<long long>;
using pii = pair<long long, long long>;
const signed INF_ = 1001001001;
const long long INF = 1001001001001001001LL;
const long long DX[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0},
                DY[9] = {-1, 0, 1, 0, -1, 1, 1, -1, 0};
template <class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto i = (begin(v)); i != (end(v)); ++i)
    os << *i << (i == end(v) - 1 ? "" : " ");
  return os;
}
template <class T>
istream &operator>>(istream &is, vector<T> &v) {
  for (auto i = (begin(v)); i != (end(v)); ++i) is >> *i;
  return is;
}
template <class T, class U>
istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}
template <class T, class U>
bool chmax(T &a, const U &b) {
  return a < b ? a = b, 1 : 0;
}
template <class T, class U>
bool chmin(T &a, const U &b) {
  return a > b ? a = b, 1 : 0;
}
template <class T>
void PSUM(T &c) {
  partial_sum(begin(c), end(c), begin(c));
}
template <class T>
using heap = priority_queue<T, vector<T>, greater<T>>;
struct before_main_function {
  before_main_function() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << setprecision(15) << fixed;
  }
} before_main_function;
signed main() {
  long long N, M;
  cin >> N >> M;
  vector<vector<long long>> g(N);
  vector<long long> deg(N);
  for (long long i = 0, ilen = (long long)(M); i < ilen; ++i) {
    long long a, b;
    cin >> a >> b;
    a--, b--;
    g[a].push_back(b);
    g[b].push_back(a);
    deg[a]++;
    deg[b]++;
  }
  vector<pii> ans;
  vector<bool> vis(N);
  {
    queue<long long> q;
    long long st = max_element(begin(deg), end(deg)) - begin(deg);
    q.push(st);
    vis[st] = true;
    while (q.size()) {
      long long v = q.front();
      q.pop();
      for (auto &&w : g[v]) {
        if (vis[w]) continue;
        vis[w] = true;
        ans.push_back({v + 1, w + 1});
        q.push(w);
      }
    }
  }
  for (auto &&p : ans) {
    cout << p.first << " " << p.second << endl;
  }
  return (0 ^ 0 ^ 0);
}
