#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define fs first
#define sc second
#define pb push_back
const int maxn=5e5;
set<int> adj[maxn+1];
int pre[maxn+1],x;
bool vis[maxn+1];
bool dfs(int v){
vis[v]=1;
for(int i:adj[v])if(i!=pre[v]){
if(vis[i]){
pre[i]=v;
x=v;
return 1;
}else{
pre[i]=v;
if(dfs(i))return 1;
}
}
return 0;
}
void solve() {
int n,m;
cin>>n>>m;
for(int i=0;i<m;i++){
int u,v;
cin>>u>>v;
adj[u].insert(v);
adj[v].insert(u);
}
vector<vector<int>> ans;
for(int i=1;i<=n;i++){
while(!adj[i].empty()){
memset(vis,0,sizeof(vis));
pre[i]=0;
dfs(i);
ans.push_back({});
ans.back().push_back(x);
int c=x;
while(pre[c]!=x){
adj[c].erase(pre[c]);
adj[pre[c]].erase(c);
c=pre[c];
ans.back().push_back(c);
}
adj[ans.back().back()].erase(ans.back()[0]);
adj[ans.back()[0]].erase(ans.back().back());
}
}
for(auto v:ans){
for(int i:v)cout<<i<<' ';
cout<<'\n';
}
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
