#include <bits/stdc++.h>
using namespace std;
using ll=long long;

struct e{
    int a,b;
    bool vis=false;
};
vector<e> edges;
vector<vector<int>> g;

void dfs(int v){
    for (int _to : g[v]){
        e &to = edges[_to];
        if (to.vis) continue;
        if (to.b==v) swap(to.a,to.b);
        to.vis=true;
        cout<<to.a<<" "<<to.b<<"\n";
        dfs(to.b);
    }
}


int main(){
    int n,m;
    cin>>n>>m;
    g.resize(n+1);
    edges.resize(m+1);
    for (int i=1;i<=m;i++){
        int a,b;
        cin>>a>>b;
        edges[i] = {a,b,false};
        g[a].push_back(i);
        g[b].push_back(i);
    }
    dfs(0);
}