#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;
typedef int ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ii> vii;
typedef vector<vii> wgraf;
typedef pair<int,ii> edge;
typedef vector <ll> vl;
typedef pair <ll, ll> LL;
typedef vector <LL> vll;
#define UNVISITED 0
#define VISITED 1
#define pb push_back
#define F first
#define S second
ll n, m, u, v, visto[500005], cone[500005];
vll grafo[500005];
bool vale = false, puede[500005];
void dfs(ll origen, ll nodo, ll aux) {
for (auto i : grafo[nodo]) {
if (puede[i.S] == true && visto[i.F] != aux) {
puede[i.S] = false;
visto[i.F] = aux;
if (i.F == origen) {
cout << nodo << " ";
vale = true;
return;
}
dfs(origen, i.F, aux);
if (vale == true) {
cout << nodo << " ";
return;
}
puede[i.S] = true;
}
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
for (ll i = 0; i < n; i++) visto[i] = 0;
for (ll i = 0; i < m; i++){
cin >> u >> v;
grafo[u].pb({v, i});
grafo[v].pb({u, i});
puede[i] = true;
cone[i] = u;
}
ll cnt = 0;
for (ll i = 0; i < m; i++) {
if (puede[i] == true) {
vale = false;
cnt++;
dfs(cone[i], cone[i], cnt);
cout << "\n";
}
}
}
