#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "../Library/debug.h"
#else
#define dbg(x...)
#endif
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) for (int i = 0; i < (a); ++i)
#define FORd(i, a, b) for (int i = (b) - 1; i >= (a); --i)
#define F0Rd(i, a) for (int i = (a) - 1; i >= 0; --i)
#define trav(a, x) for (auto& a : x)
#define f first
#define s second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
const char nl = '\n';
const int INF = 1e9;
const int MOD = 1e9 + 7;
void solve(){
int n,m;
cin>>n>>m;
vector<vi> adj(n);
vi e(m);
vb vis(m);
F0R(i,m){
int a,b;
cin>>a>>b;
a--,b--;
e[i]=a^b;
adj[a].pb(i);
adj[b].pb(i);
}
vi path;
function<void(int)> euler=[&](int v)->void{
while(!adj[v].empty()){
int id=adj[v].back();
adj[v].pop_back();
if(vis[id])continue;
vis[id]=true;
euler(e[id]^v);
}
path.pb(v);
};
euler(0);
vb v_(n);
vi tmp;
trav(i,path){
tmp.pb(i);
if(v_[i]){
cout<<tmp.back()+1<<" ";
tmp.pop_back();
while(!tmp.empty()&&tmp.back()!=i){
cout<<tmp.back()+1<<" ";
v_[tmp.back()]=false;
tmp.pop_back();
}
cout<<nl;
assert(tmp.back()==i);
tmp.pop_back();
v_[i]=false;
}
else{
v_[i]=true;
}
}
}
int32_t main(){
ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int TC = 1;
// cin >> TC;
while(TC--){
solve();
}
return 0;
}
