#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<map<int, int>> cing;
vector<set<int>> g;
vector<vector<int>> ans;
vector<bool> used;
vector<int> cur;
set<pair<int, int>> vert;
void dfs(int v) {
used[v] = 1;
cur.push_back(v);
for (auto u : g[v]) {
if (vert.find({v, u}) == vert.end()) {
continue;
}
vert.erase({v, u});
vert.erase({u, v});
if (used[u]) {
vector<int> res;
while(!cur.empty() && cur.back() != u) {
res.push_back(cur.back());
used[cur.back()] = 0;
cur.pop_back();
}
if (!cur.empty()) {
used[cur.back()] = 0;
res.push_back(cur.back());
cur.pop_back();
}
ans.push_back(res);
if (!cur.empty()) {
dfs(u);
} else {
dfs(v);
}
} else {
dfs(u);
cur.push_back(v);
}
}
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m;
cin >> n >> m;
used.resize(n);
g.resize(n);
cing.resize(n);
for (int i = 0; i < m; i++) {
int v, u;
cin >> v >> u;
if (v > u)
swap(u, v);
cing[v - 1][u - 1]++;
}
for (int v = 0; v < n; v++) {
for (auto [u, cn] : cing[v]) {
while (cn > 1) {
cn -= 2;
ans.push_back({v, u});
}
if (cn == 1) {
g[v].insert(u);
g[u].insert(v);
vert.insert({v, u});
vert.insert({u, v});
}
}
}
dfs(0);
for (auto s : ans) {
for (auto el : s) {
cout << el + 1 << ' ';
}
cout << '\n';
}
}
