#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define all(x) x.begin(), x.end()
#define pb push_back
#define sz(x) (int)(x.size())
#define ll long long
#define fi first
#define se second
#define lbd lower_bound
#define ubd upper_bound
template <typename T>
using ordered_set = tree<T, null_type,
less<T>, rb_tree_tag,
tree_order_statistics_node_update>;
const int MOD = 1e9 + 7;
const double eps = 1e-10;
const long long INF = 1e18;
const int N = 2e5 + 10;
struct Euler_Path {
int n, m;
vector<vector<pair<int, int>>> adj;
vector<int> its;
vector<pair<int, int>> ret, s;
vector<int> path;
vector<bool> vis;
void init(int _n, int _m) {
n = _n;
m = _m;
adj.resize(n);
its.resize(n);
vis.resize(m);
s = {{0, -1}};
}
void add_edge(int u, int v, int id) {
adj[u].pb({v, id});
adj[v].pb({u, id});
}
vector<int> euler_dfs() {
while (!s.empty()) {
int x = s.back().first;
while (its[x] < sz(adj[x]) && vis[adj[x][its[x]].second]) its[x]++;
if (its[x] == sz(adj[x])) {
if (!ret.empty() && ret.back().second != x) return path;
ret.pb(s.back());
s.pop_back();
} else {
s.pb({adj[x][its[x]].first, x});
vis[adj[x][its[x]].second] = 1;
}
}
if (sz(ret) != m + 1) return path;
for (const auto &[v, id]: ret) {
path.pb(v);
}
reverse(all(path));
return path;
}
} idk;
void solve() {
int n, m;
cin >> n >> m;
idk.init(n, m);
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
--u, --v;
idk.add_edge(u, v, i);
}
idk.euler_dfs();
vector<int> ans = idk.path;
vector<int> cycles;
bool vis[n] = {};
vector<vector<int>> fin;
for (const auto &it : ans) {
if (vis[it]) {
vector<int> curr;
curr.pb(it);
while (cycles.back() != it) {
curr.pb(cycles.back());
vis[cycles.back()] = 0;
cycles.pop_back();
}
fin.pb(curr);
} else {
vis[it] = 1;
cycles.pb(it);
}
}
for (const auto &v : fin) {
for (const auto &it : v) cout << it + 1 << ' ';
cout << '\n';
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int tt = 1;
//cin >> tt;
while (tt--) {
solve();
cout << '\n';
}
return 0;
}
