// https://oj.uz/problem/view/BOI14_postmen
#include <bits/stdc++.h>
using namespace std;
vector<int> et = {};
vector<vector<int>> ets = {};
void clean(vector<int> xs) {
unordered_map<int, bool> lx;
stack<int> s;
// for (int x : xs) {
// cout << x << " ";
// }
// cout << endl;
for (int i = 0; i < xs.size(); i++) {
int x = xs[i];
// cout << i << " " << x << endl;
if (i == xs.size() -1) {
vector<int> et = {};
while (s.size() > 0) {
et.push_back(s.top());
// cout << s.top() << endl;
s.pop();
}
// cout << "A" << endl;
ets.push_back(et);
} else if (lx.find(x) != lx.end() && lx[x]) {
vector<int> oxs = {x, };
while (true) {
int y = s.top();
oxs.push_back(y);
// cout << y << endl;
if (y == x) {
break;
} else {
lx[y] = false;
s.pop();
}
}
clean(oxs);
} else {
lx[x] = true;
s.push(x);
}
}
}
void dfs(vector<unordered_set<int>> &to, int i) {
while (to[i].size()) {
int j = *to[i].begin();
to[i].erase(j);
to[j].erase(i);
dfs(to, j);
}
et.push_back(i);
}
int main() {
int n, m;
cin >> n >> m;
vector<unordered_set<int>> to(n, unordered_set<int> {});
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
a--; b--;
to[a].insert(b);
to[b].insert(a);
}
dfs(to, 0);
// for (int a : et) {
// cout << a+1 << " ";
// }
// cout << endl;
clean(et);
for (auto et : ets) {
// cout << "B" << endl;
for (int x : et) {
cout << x+1 << " ";
}
cout << endl;
}
}
