#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<vector<pair<int, int>>> g;
vector<bool> seen;
vector<int> seq;
void dfs(int k) {
while (!g[k].empty()) {
if (seen[g[k].back().second] == 1) {
g[k].pop_back();
continue; // if edge has already been deleted
}
seen[g[k].back().second] = 1;
int a = g[k].back().first;
g[k].pop_back();
dfs(a);
}
seq.push_back(k);
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, m;
cin >> n >> m;
g = vector<vector<pair<int, int>>> (n);
seen = vector<bool> (m, 0);
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
a--; b--;
g[a].push_back({b, i});
g[b].push_back({a, i});
}
//dont need to check if possible bc question says is possible
dfs(0);
//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";
}
}
