#include <bits/stdc++.h>
using namespace std;
#define SPEED ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
#define pb push_back
#define fi first
#define se second
#define endl "\n"
#define ALL(x) x.begin(), x.end()
#define sz(x) x.size()
#define intt long long
const intt mxN = 2e5 + 5;
const intt inf = 1e18;
const intt mod = 1e9 + 7;
vector<vector<pair<intt,intt>>> graph;
vector<intt> usedE(mxN), usedN(mxN);
vector<intt> path;
vector<vector<intt>> ans;
void dfs(intt node) {
if(usedN[node]) {
vector<intt> pushla;
while(not path.empty() && path.back() != node) {
usedN[path.back()] = 0;
pushla.pb(path.back());
path.pop_back();
}
pushla.pb(node);
ans.pb(pushla);
} else {
usedN[node] = 1;
path.pb(node);
}
intt f = 0;
if(graph[node].empty()) {
return;
}
while(usedE[graph[node].back().se]) {
graph[node].pop_back();
if(graph[node].empty()) {
f = 1; break;
}
}
if(f) return;
usedE[graph[node].back().se] = 1;
dfs(graph[node].back().fi);
}
void solve() {
intt N, M;
cin >> N >> M;
graph.assign(N + 1, vector<pair<intt,intt>>{});
for(intt i = 0; i < M; i++) {
intt a, b;
cin >> a >> b;
graph[a].pb({b,i});
graph[b].pb({a,i});
}
for(intt i = 1; i <= N; i++) {
if(!graph[i].empty()) dfs(i);
}
for(vector<intt> &P : ans) {
for(intt i : P) cout << i << " ";
cout << endl;
}//edu
}
signed main() {
SPEED;
intt tst = 1;
// cin >> tst;
while (tst--) {
solve();
}
}
