#include <bits/stdc++.h>
using namespace std;
const int MAXN = 5e5;
struct Edge {
int v, id;
Edge(int _v=0, int _id=0): v(_v), id(_id) {}
};
vector<Edge> adj[MAXN];
bool mark[MAXN];
bool in_eulerian[MAXN];
vector<int> eulerian;
void dfs(int v) {
while (!adj[v].empty()) {
Edge ed = adj[v].back();
adj[v].pop_back();
if (mark[ed.id]) continue;
mark[ed.id] = true;
dfs(ed.v);
}
if (in_eulerian[v]) {
int i = -1;
while (i != v) {
i = eulerian.back();
eulerian.pop_back();
in_eulerian[i] = false;
cout << i+1 << ' ';
}
cout << endl;
}
in_eulerian[v] = true;
eulerian.push_back(v);
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int n, m; cin >> n >> m;
for (int i=0; i<m; i++) {
int u, v; cin >> u >> v;
u--; v--;
adj[u].push_back(Edge(v, i));
adj[v].push_back(Edge(u, i));
}
for (int i=0; i<n; i++) {
if (!adj[i].empty()) dfs(i);
}
return 0;
}
