#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
int x, y;
vector<set<int>> adj(n);
for (int i = 0; i < m; i++) {
cin >> x >> y; x--; y--;
adj[x].insert(y);
adj[y].insert(x);
}
// hierholzer
set<int> nodes;
for (int i = 0; i < n; i++) {
nodes.insert(i);
}
vector<vector<int>> ans;
while (nodes.size()) {
int start = *nodes.begin();
stack<pii> sta;
sta.push({start, -1});
vector<bool> vis(n, 0);
while (sta.size()) {
int node, par;
tie(node, par) = sta.top();
if (vis[node]) {
break;
}
vis[node] = 1;
int next = *adj[node].begin();
if (next == par) {
next = *(++((adj[node].begin())));
}
sta.push({next, node});
}
vector<int> vec;
int end = sta.top().first;
int nod, las;
tie(nod, las) = sta.top();
sta.pop();
do {
adj[nod].erase(las);
adj[las].erase(nod);
if (adj[nod].size() == 0) {
nodes.erase(nod);
}
if (adj[las].size() == 0) {
nodes.erase(las);
}
tie(nod, las) = sta.top();
sta.pop();
vec.push_back(nod);
} while (nod != end);
ans.push_back(vec);
}
for (vector<int> vec : ans) {
for (int x : vec) {
cout << x+1 << " ";
}
cout << "\n";
}
cout << flush;
return 0;
}
