#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
int n,m;
set<int> roads[500005];
bool vis[500005];
vector<int> curr;
vector<vector<int>> ans;
void euler(int x){
if(vis[x]){
curr = {x};
return;
}
vis[x] = true;
while(roads[x].size()>0){
int p = *roads[x].begin();
roads[x].erase(p);
roads[p].erase(x);
euler(p);
if(curr.size()>0 and curr[0]!=x){
curr.push_back(x);
vis[x] = false;
return;
}
else if(curr[0]==x){
ans.push_back(curr);
curr.clear();
}
}
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
for(int i=1;i<=m;i++){
int a,b;
cin >> a >> b;
roads[a].insert(b);
roads[b].insert(a);
}
for(int i=1;i<=n;i++){
if(roads[i].size()>0){
euler(i);
}
}
for(vector<int> i:ans){
for(int j:i){
cout << j << " ";
}
cout << "\n";
}
return 0;
}
