#include <bits/stdc++.h>
#define len(x) (int)(x).size()
#define range(i, x, y) for(int i=x; i<y; i++)
#define sws ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define vint vector<int>
#define vll vector<long long>
#define vstr vector<string>
#define ll long long
#define F first
#define S second
#define pb push_back
#define pf push_front
#define del(a, n) (a).erase(a.begin()+(n))
#define mp make_pair
#define all(a) (a.begin(), a.end())
const int MAX = 1e6;
using namespace std;
vint sol;
unordered_multiset<int> gra[MAX];
void dfs(int node)
{
while(gra[node].size())
{
int v;
for(auto x : gra[node]){
v = x;
break;
}
gra[node].erase(v);
gra[v].erase(node);
dfs(v);
}
sol.pb(node);
}
bool vs[MAX];
void decompose() {
stack<int> cur;
vector<vint> re;
for(int u:sol) {
if(!vs[u]) {
cur.push(u);
vs[u] = 1;
}
else {
vint cyc;
while(vs[u]) {
cyc.pb(cur.top());
vs[cur.top()] = 0;
cur.pop();
}
for(auto x : cyc){
cout << x << " ";
}
cout << endl;
cur.push(u);
vs[u] = 1;
}
}
}
int main(){
sws
int n, m;
cin >> n >> m;
for(int i=0; i<m; i++){
int u, v;
cin >> u >> v;
gra[u].insert(v);
gra[v].insert(u);
}
dfs(1);
decompose();
}
