#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i,l,r) for(int i = (l); i < r; i++)
#define per(i,r,l) for(int i = (r); i >= l; i--)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define pb push_back
#define ff first
#define ss second
const ll mod = 1e9 + 7,maxlg = 22, maxn = 5e5 + 5, inf = 1e9 + 5, p = 9973;
bool vis[maxn];
int ptr[maxn];
vector<pair<int, int>> adj[maxn];
vector<int> tour;
void dfs(int r){
while(ptr[r] != sz(adj[r])){
int id = adj[r][ptr[r]].ss, c = adj[r][ptr[r]].ff;
ptr[r]++;
if(!vis[id]){
vis[id] = 1;
dfs(c);
}
}
tour.pb(r);
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
rep(i,0,m){
int u, v; cin >> u >> v;
u--, v--;
adj[u].pb({v, i});
adj[v].pb({u, i});
}
dfs(0);
vector<int> st;
vector<bool> in_st(n);
rep(i,0,sz(tour)){
if(in_st[tour[i]]){
cout << tour[i] + 1 << ' ';
while(st.back() != tour[i]){
cout << st.back() + 1 << ' ';
in_st[st.back()] = 0;
st.pop_back();
}
cout << '\n';
}else{
st.pb(tour[i]);
in_st[tour[i]] = 1;
}
}
return 0;
}
