#include <bits/stdc++.h>
#define fi first
#define se second
#define vi_a vector<int>a;
#define p_b push_back
#define ll long long
#define ld long double
#define pll pair<long long,bool>
#define pii pair<int,int>
#define m_p make_pair
#define fast_io cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(0);
#define all(x) x.begin(),x.end()
#define sset ordered_set
#define sqr(x) (x)*(x)
#define pw(x) (1ll << x)
#define sz(x) (int)x.size()
#define endl "\n"

using namespace std;
vector<vector<ll>>a(0,vector<ll>(0));
vector<bool>used;
vector<pll>order(0);
void dfs(ll v){
    used[v]=1;
    for(ll &z : a[v]){
        if(!used[z]){
            cout<<z+1<<" "<<v+1<<endl;
            order.push_back(m_p(z,v));
            cout<<order.back().fi+1<<" "<<order.back().se+1<<endl;
            dfs(z);
        }
    }
}
int main()
{
    fast_io;
    ll n,m;
    cin>>n>>m;
    a.resize(n);
    used.assign(n,0);
    ll v,u;
    for(ll i=0;i<m;i++){
        cin>>v>>u;
        v--;u--;
        a[v].p_b(u);
        a[u].p_b(v);
    }
    for(ll i=0;i<n;i++){
        if(!used[i]){
            dfs(i);
            break;
        }
    }
    cout<<endl;
    for(ll i=0;i<order.size();i++){
        cout<<order[i].fi<<" "<<order[i].se<<endl;
    }
    return 0;
}