#include <bits/stdc++.h>
using namespace std;;
#define ll long long
#define ar array
#define ld long double
#define int long long
#define all(v) v.begin(), v.end()
const int N = 2e5 + 20;
const int K = 469;
const int LOG = 26;
const int INF = 1e12;
int MOD = 998244353;
int n, m;
vector<ar<int,2>> g[N];
vector<int> ord;
bool vis[N];
void dfs(int x){
while(g[x].size()){
auto [u, i] = g[x].back();
g[x].pop_back();
if(!vis[i]){
vis[i] = 1;
dfs(u);
}
}
ord.push_back(x);
}
void orz(){
cin>>n>>m;
for(int i = 0;i < m;i++){
int a, b;
cin>>a>>b;
--a, --b;
g[a].push_back({b, i});
g[b].push_back({a, i});
}
dfs(0);
stack<int> s;
bool in[n] = {0};
for(auto u: ord){
if(in[u]){
cout<<u + 1<<" ";
while(s.top() != u){
in[s.top()] = 0;
cout<<s.top() + 1<<" ";
s.pop();
}
s.pop();
in[u] = 0;
cout<<'\n';
}
s.push(u);
in[u] = 1;
}
}
signed main(){ios_base::sync_with_stdio(false);cin.tie(0);
int t;
//cin>>t;
t = 1;
while(t--)orz();
}
