#include <fstream>
#include <vector>
using namespace std;
ifstream f("mesaj4.in");
ofstream g("mesaj4.out");
int N,M;
bool Use[100005];
vector < pair<int,int> > Sol;
vector <int> G[100005];
void Read()
{
int i;
f>>N>>M;
for(int i=1;i<=M;i++)
{
int x,y;
f>>x>>y;
G[x].push_back(y);
G[y].push_back(x);
}
}
void DFS(int node)
{
Use[node]=1;
for(int i=0;i<G[node].size();i++)
{
int neighb=G[node][i];
if(Use[neighb]==0)
{
Sol.push_back(make_pair(node,neighb));
DFS(neighb);
}
}
}
int main()
{
Read();
DFS(1);
for(int i=0;i<Sol.size();i++)
g<<Sol[i].first<<" "<<Sol[i].second<<"\n";
for(int i=Sol.size()-1;i>=0;i--)
g<<Sol[i].second<<" "<<Sol[i].first<<"\n";
return 0;
}