#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
const int INFMEM = 63;
const int INF = 1061109567;
const long long LINF = 4557430888798830399LL;
const double DINF = numeric_limits<double>::infinity();
const long long MOD = 1000000007;
const int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dy[8] = {0, 1, 0, -1, 1, -1, 1, -1};
const double PI = 3.141592653589793;
inline void fastll(long long &input_number) {
  input_number = 0;
  int ch = getchar_unlocked();
  int sign = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') sign = -1;
    ch = getchar_unlocked();
  }
  while (ch >= '0' && ch <= '9') {
    input_number = (input_number << 3) + (input_number << 1) + ch - '0';
    ch = getchar_unlocked();
  }
  input_number *= sign;
}
inline void open(string a) {
  freopen((a + ".in").c_str(), "r", stdin);
  freopen((a + ".out").c_str(), "w", stdout);
}
inline void fasterios() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
long long n, m;
bool vis[200005];
queue<long long> antri;
vector<long long> edge[200005];
void bfs(long long pos) {
  for (int i = 0; i < edge[pos].size(); i++) {
    long long nx = edge[pos][i];
    if (vis[nx]) continue;
    vis[nx] = 1;
    cout << pos << " " << nx << '\n';
    antri.push(nx);
  }
}
int main() {
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    long long u, v;
    cin >> u >> v;
    edge[u].push_back(v);
    edge[v].push_back(u);
  }
  long long idx = 0;
  long long now = 0;
  for (int i = 1; i <= n; i++) {
    if (now < edge[i].size()) {
      now = edge[i].size();
      idx = i;
    }
  }
  antri.push(idx);
  vis[idx] = 1;
  while (!antri.empty()) {
    long long tmp = antri.front();
    antri.pop();
    bfs(tmp);
  }
  return 0;
}
