#include <iostream>

using namespace std;

void dfs(int **matr, int *viewed, int n, int v) {
    viewed[v] = 1;

    for (int j = 0; j < n; ++j) {
        if (matr[v][j] and !viewed[j]) {
            cout << v+1 << " " << j+1 << endl;
            dfs(matr, viewed, n, j);
        }

    }
}

int main() {
    int n, m;
    cin >> n;
    cin >> m;

    // Initialization
    int **matr = new int *[n];
    for (int i = 0; i < n; ++i) { matr[i] = new int[n]; for(int j = 0; j < n; ++j){matr[i][j] = 0;}}
    int *viewed = new int[n];
    for (int i = 0; i < n; ++i) { viewed[i] = 0; }
    // End of Initialization (Like "End of Civilization")
    // {Hello from Nibiru (https://utro.ru/internet/2019/05/20/1400576.shtml)}

    int I, J;
    for (int i = 0; i < m; ++i) {
        cin >> I >> J;
        matr[I-1][J-1] = 1;
        matr[J-1][I-1] = 1;
    }

    dfs(matr, viewed, n, 0);
}