#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MXN = 5e5 + 5;
int n, m;
set<int> adj[MXN];
int used[MXN], par[MXN];
vector<int> o;
void dfs(int a)
{
while (!adj[a].empty())
{
int v = *adj[a].begin();
adj[a].erase(adj[a].begin());
adj[v].erase(a);
dfs(v);
}
o.push_back(a);
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= m; i++)
{
int u, v;
cin >> u >> v;
adj[u].insert(v);
adj[v].insert(u);
}
dfs(1);
vector<vector<int>> res;
map<int, int> mp;
set<int> s;
for (int i = 0; i < o.size(); i++)
{
if (mp.find(o[i]) != mp.end())
{
vector<int> v;
int l = mp[o[i]];
auto it = s.begin();
while ((it = s.lower_bound(l)) != s.end())
{
v.push_back(o[*it]);
mp.erase(o[*it]);
s.erase(it);
}
res.push_back(v);
}
mp[o[i]] = i;
s.insert(i);
}
for (vector<int> &a : res)
{
for (int &i : a) cout << i << ' ';
cout << '\n';
}
}
