#include<bits/stdc++.h>
using namespace std;
const int maxn=5e5+10;
vector<pair<int,int>> v[maxn];
vector<int> cycle;
int last[maxn], l[maxn], r[maxn], marc[maxn];
void dfs(int u){
while(!v[u].empty()){
int a=v[u].back().first, id=v[u].back().second;
v[u].pop_back();
if(marc[id]) continue;
marc[id]=1;
dfs(a);
}
cycle.push_back(u);
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
int n, m; cin >> n >> m;
for(int i=1;i<=m;i++){
int a, b; cin >> a >> b;
v[a].push_back({b,i}); v[b].push_back({a,i});
}
dfs(1);
memset(last,-1,sizeof(last));
for(int i=1;i<cycle.size()-1;i++){
l[i]=i-1; r[i]=i+1;
}
r[0]=1;
if(cycle.size()>=2) l[cycle.size()-1]=cycle.size()-2;
for(int i=0;i<cycle.size();i++){
if(last[cycle[i]]!=-1){
int j=last[cycle[i]], at=l[j];
while(j<i){
cout << cycle[j] << " ";
last[cycle[j]]=-1;
cycle[j]=-1;
j=r[j];
}
r[at]=j; l[j]=at;
cout << endl;
}
last[cycle[i]]=i;
}
}
