#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
typedef long double ld;
const ll inf = 1e9;
const ld eps = 1e-8;
vector<multiset<int>> g;
vector<vector<int>> ans;
vector<bool> used;
vector<int> cur;
set<int> stcur;
vector<int> res;
void dfs(int v) {
if (stcur.find(v) != stcur.end()) {
res.clear();
while(cur.back() != v) {
stcur.erase(cur.back());
res.push_back(cur.back());
cur.pop_back();
}
stcur.erase(cur.back());
res.push_back(cur.back());
cur.pop_back();
ans.push_back(res);
}
cur.push_back(v);
stcur.insert(v);
if(!g[v].empty()) {
auto t = g[v].begin();
int u = *t;
g[v].erase(t);
g[u].erase(g[u].find(v));
dfs(u);
}
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m;
cin >> n >> m;
used.resize(n);
g.resize(n);
for (int i = 0; i < m; i++) {
int v, u;
cin >> v >> u;
g[v - 1].insert(u - 1);
g[u - 1].insert(v - 1);
}
for (int i = 0; i < n; i++) {
if (!g[i].empty())
dfs(i);
}
for (auto s : ans) {
for (auto el : s) {
cout << el + 1 << ' ';
}
cout << '\n';
}
}
