#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int>> graph[500001];
bool visited[500001], used[500001];
int nxt[500001];
void dfs(int node) {
if (visited[node]) {
while (visited[node]) {
visited[node] = false;
cout << node << ' ';
node = nxt[node];
}
cout << '\n';
}
while (graph[node].size()) {
int c, idx;
tie(c, idx) = graph[node].back();
graph[node].pop_back();
if (!used[idx]) {
used[idx] = true;
visited[node] = true;
nxt[node] = c;
dfs(c);
}
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
graph[a].push_back({b, i});
graph[b].push_back({a, i});
}
dfs(1);
return 0;
}
