#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast,inline") // Ofast = O3,fast-math,allow-store-data-races,no-protect-parens
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("bmi,bmi2,lzcnt,popcnt") // bit manipulation
#pragma GCC target("movbe") // byte swap
#pragma GCC target("aes,pclmul,rdrnd") // encryption
#pragma GCC target("avx,avx2,f16c,fma,sse3,ssse3,sse4.1,sse4.2")
typedef long long ll;
#define rep(i, a, b) for (int i = (a); i < int(b); i++)
#define rrep(i, a, b) for (int i = (a) - 1; i >= int(b); i--)
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define pb push_back
inline void fast() { ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); }
ll INF = 1000000000;
ll mod = 1e9 + 7;
#define int ll
#define float double
//
int N, M;
vector<vector<pii>> graph;
vector<bool> visited_node, visited_edge;
vector<vector<int>> tours;
vector<int> tour;
int dfs(int node) {
// cerr << "enter " << node + 1 << "\n";
visited_node[node] = true;
int ret = -1;
while (true) {
rrep(i, graph[node].size(), 0) {
// cerr << "edge " << graph[node][i].first << " " << graph[node][i].second + 1 << "\n";
if (visited_edge[graph[node][i].first]) graph[node].pop_back();
else if (visited_node[graph[node][i].second]) {
visited_edge[graph[node][i].first] = true;
ret = graph[node][i].second;
graph[node].pop_back();
break;
}
else {
visited_edge[graph[node][i].first] = true;
int n = graph[node][i].second;
graph[node].pop_back();
ret = dfs(n);
break;
}
}
if (ret == node) {
tour.pb(node);
tours.pb(tour);
tour.clear(); //
ret = -1;
}
else if (ret != -1) {
tour.pb(node);
break;
}
if (graph[node].size() == 0) return -2;
}
//
visited_node[node] = false;
// cerr << "leaving " << node + 1 << "\n";
return ret;
}
int32_t main()
{
fast();
cin >> N >> M;
graph.assign(N, {});
int a, b;
int e = 0;
rep(i,0,M) {
cin >> a >> b;
a--; b--;
graph[a].pb({e, b});
graph[b].pb({e, a});
e++;
}
// assert even
visited_node.assign(N, false);
visited_edge.assign(M, false);
rep(i,0,N) {
while (graph[i].size() > 0) {
dfs(i);
}
}
rep(i,0,tours.size()) {
rep(j,0,tours[i].size()) {
cout << tours[i][j] + 1 << " ";
}
cout << "\n";
}
}
