#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
vector <pair <int, int>> graf[500005];
bool visited[500005];
bool used[500005];
vector <vector <int>> cycles;
bool novi;
void ocisti(vector <pair <int, int>> &vec){
while(!vec.empty() && used[vec.back().second]){
vec.pop_back();
}
}
void dfs(int tr){
stack <int> stek;
stek.push(tr);
visited[tr] = 1;
while(!stek.empty()){
int v = stek.top();
ocisti(graf[v]);
if(novi){
cycles.back().push_back(v);
if(cycles.back()[0] == cycles.back()[cycles.back().size()-1]){
novi = 0;
continue;
}
stek.pop();
visited[v] = 0;
continue;
}
if(graf[v].empty()){
visited[v] = 0;
stek.pop();
continue;
}
int c = graf[v].back().first;
int g = graf[v].back().second;
graf[v].pop_back();
used[g] = 1;
if(visited[c]){
cycles.push_back({});
cycles.back().push_back(c);
novi = 1;
continue;
}
else{
stek.push(c);
visited[c] = 1;
continue;
}
stek.pop();
visited[v] = 0;
}
}
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
int n, m;
cin >> n >> m;
int cnt = 0;
for(int i=1; i<=m; i++){
int a, b;
cin >> a >> b;
graf[a].push_back({b, ++cnt});
graf[b].push_back({a, cnt});
}
int tr = 1;
dfs(tr);
while(tr <= n){
dfs(tr);
if(!graf[tr].size()) tr++;
}
for(auto cycle : cycles){
cycle.pop_back();
for(auto c : cycle) cout << c << " ";
cout << "\n";
}
return 0;
}
