#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, m;
cin >> n >> m;
vector<set<int>> g(n);
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
a--; b--;
g[a].insert(b);
g[b].insert(a);
}
//dont need to check if possible bc question says is possible
vector<int> seq;
stack<int> stak;
stak.push(0);
while (!stak.empty()) {
int u = stak.top();
//~ cout << u+1 << endl;
if (g[u].size() > 0) { //if still neighbours
int v = *g[u].begin();
stak.push(v);
g[u].erase(v); //erase edge from both sides
g[v].erase(u);
} else { //need to add to tour
stak.pop();
seq.push_back(u);
//~ cout << u+1 << " ";
}
}
//now make tours out of this tour
vector<vector<int>> ans;
vector<int> count(n, 0);
stack<int> s; //has verteces which we can remove as appropriate
for (int i : seq) {
if (count[i] > 0) {
ans.push_back({});
while (s.top() != i) {
count[s.top()]--;
ans[ans.size()-1].push_back(s.top());
s.pop();
}
ans[ans.size()-1].push_back(i);
} else {
count[i]++;
s.push(i);
}
}
if (s.size() > 1) {
ans.push_back({});
while (!s.empty()) {
ans[ans.size()-1].push_back(s.top());
s.pop();
}
}
for (auto i : ans) {
for (int j : i) {
cout << j+1 << " ";
}
cout << "\n";
}
}
