#include <bits/stdc++.h>
using namespace std;
pair <int , int> muchie[1000000];
int capat[500001] , locatie[500001] , stiva[500001];
bool blocat[500000];
inline void Parcurgere (const int nod)
{
for (int& indice = capat[nod] ; indice != -1 ; ) {
if (blocat[indice >> 1])
{ indice = muchie[indice].second; }
else
{
const int vecin = muchie[indice].first;
blocat[indice >> 1] = true;
indice = muchie[indice].second;
Parcurgere(vecin);
}
}
if (!locatie[nod])
{
stiva[++stiva[0]] = nod;
locatie[nod] = stiva[0];
}
else
{
for (int indice = locatie[nod] + 1 ; indice <= stiva[0] ; indice++)
{
cout << stiva[indice] << ' ';
locatie[stiva[indice]] = 0;
}
cout << nod << '\n';
stiva[0] = locatie[nod];
}
}
int main()
{
ios :: sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int numar_noduri , numar_muchii;
cin >> numar_noduri >> numar_muchii;
for (int indice = 1 ; indice <= numar_noduri ; indice++)
{ capat[indice] = -1; }
for (int indice = 0 ; indice < numar_muchii ; indice++)
{
int nod[2]; cin >> nod[0] >> nod[1];
muchie[2 * indice] = {nod[0] , capat[nod[1]]}; capat[nod[1]] = 2 * indice;
muchie[2 * indice + 1] = {nod[1] , capat[nod[0]]}; capat[nod[0]] = 2 * indice + 1;
}
Parcurgere(1);
for (int indice = 1 ; indice <= stiva[0] ; indice++)
{ cout << stiva[indice] << ' '; }
return 0;
}
