#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef vector<vii> vvi;
bitset<1000000> mp;
vvi g;
vi path;
vi vis;
vi indeg;
int x=-1;
void dfs(int u){
path.push_back(u);
if(vis[u]==true){
x = u;
cout<<u<<" ";
vis[u]=false;
return;
}
vis[u]=true;
for(auto v: g[u]){
vis[u]=true;
if(mp[v.second]!=1){
mp[v.second]=1;
indeg[u]--;
indeg[v.first]--;
dfs(v.first);
if(x!=-1 && x!=u){
// cout<<u<<endl;
cout<<u<<" ";
vis[u]=false;
return;
}
if(x!=-1 && x==u){
vis[u]=false;
cout<<endl;
x=-1;
}
}
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n,m;
cin>>n>>m;
g.resize(n+1,vii());
vis.resize(n+1,0);
indeg.resize(n+1,0);
for(int i=0; i<m; i++){
int a,b;
cin>>a>>b;
if(a>b) swap(a,b);
mp[i] = 0;
indeg[a]++;
indeg[b]++;
g[a].push_back({b,i});
g[b].push_back({a,i});
}
for(int i=1; i<=n; i++){
if(indeg[i]>0) dfs(i);
}
}
