#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define tiii tuple<int,int,int>
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<set<int>> adj(n);
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
a--; b--;
adj[a].insert(b);
adj[b].insert(a);
}
vector<int> trav;
set<int> occ;
set<int> left;
for (int i = 0; i < n; i++) {
left.insert(i);
}
stack<int> S;
S.push(0);
vector<vector<int>> paths;
while (S.size()) {
int v = S.top();
if (occ.count(v)) {
vector<int> p;
p.push_back(S.top()); S.pop();
do {
occ.erase(S.top());
p.push_back(S.top()); S.pop();
} while (S.top() != v);
paths.push_back(p);
if (adj[S.top()].size() == 0) {
S.pop();
}
if (S.empty() && left.size()) {
S.push(*left.begin());
}
if (S.empty()) break;
}
v = S.top();
int u = *adj[v].begin();
adj[u].erase(v);
adj[v].erase(u);
if (adj[v].size() == 0) left.erase(v);
if (adj[u].size() == 0) left.erase(u);
S.push(u);
occ.insert(v);
}
for (auto p : paths) {
for (auto v : p) {
cout << v + 1 << " ";
}
cout << endl;
}
}
