#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
// #define int long long
#define ld long double
#define ll long long
#define pii pair<int, int>
#define all(v) v.begin(), v.end()
using namespace std;
const int oo = 1e9 + 9;
const int MAX = 5e5 + 6, LOGMAX = 20, B = 400, MOD = 1e9 + 7;
int n, m;
vector<pii> g[MAX];
int vis[MAX];
vector<int> path;
void dfs(int node){
for(pii to : g[node]){
if(vis[to.second]) continue;
vis[to.second] = 1;
dfs(to.first);
}
path.push_back(node);
}
void solve(){
cin >> n >> m;
for(int i = 1; i <= m; i++){
int u, v; cin >> u >> v;
g[u].push_back({v, i});
g[v].push_back({u, i});
}
dfs(1);
memset(vis, 0, sizeof(vis));
vector<int> cur;
for(int a : path){
if(vis[a]){
while(cur.size()){
cout << cur.back() << ' ';
vis[cur.back()] = 0;
if(cur.back() == a){
cur.pop_back();
break;
}
cur.pop_back();
}
cout << '\n';
}
cur.push_back(a);
vis[a] = 1;
}
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
while(t--) solve();
}
