#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 7;
struct edge {
  int t, n;
} g[N * 2];
int head[N];
int d[N];
int cnt = 1;
void add(int f, int t) {
  g[cnt].n = head[f];
  g[cnt].t = t;
  head[f] = cnt;
  cnt++;
}
struct e {
  int f, t;
};
vector<e> v;
int vis[N];
void dfs(int d, int n) {
  bool find = false;
  vector<int> v2;
  for (int i = head[d]; i; i = g[i].n) {
    int t = g[i].t;
    if (vis[t])
      continue;
    else {
      v.push_back((e){d, t});
      vis[t] = 1;
      v2.push_back(t);
      find = true;
    }
  }
  if (!find) return;
  int len = v2.size();
  for (int i = 0; i < len; i++) {
    dfs(v2[i], n);
  }
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  int f, t, maxd = 0, maxp;
  for (int i = 0; i < m; i++) {
    cin >> f >> t;
    add(f, t);
    add(t, f);
    d[t]++;
    d[f]++;
    if (d[t] > maxd) {
      maxd = d[t];
      maxp = t;
    }
    if (d[f] > maxd) {
      maxd = d[f];
      maxp = f;
    }
  }
  vis[maxp] = 1;
  dfs(maxp, n);
  int k = v.size();
  for (int i = 0; i < k; i++) {
    cout << v[i].f << " " << v[i].t << endl;
  }
}
