#include<bits/stdc++.h>
using namespace std;
const int maxn=5e5+10;
map<pair<int,int>,int>marc;
vector<int>v[maxn], cycle, resp[maxn];
int last[maxn];
void dfs(int u){
while(!v[u].empty()){
int a=v[u].back();
v[u].pop_back();
if(marc[{u,a}]==1) continue;
marc[{u,a}]=marc[{a,u}]=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); v[b].push_back(a);
}
dfs(1);
memset(last,-1,sizeof(last));
//for(int a : cycle) cout << a << " ";
//cout << endl;
for(int i=0;i<cycle.size();i++){
if(last[cycle[i]]!=-1){
//cout << i << ": ";
for(int j=last[cycle[i]];j<i;j++){
if(cycle[j]!=-1) cout << cycle[j] << " ";
if(cycle[j]!=-1) last[cycle[j]]=-1;
cycle[j]=-1;
}
cout << endl;
}
last[cycle[i]]=i;
}
//for(int a : cycle) if(a!=-1) cout << a << " ";
//cout << endl;
}
