#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pli pair<ll, int>
#define pil pair<int, ll>
#define pdi pair<double, int>
#define pcc pair<char, char>
#define tiii tuple<int, int, int>
#define tlii tuple<int, int, int>
#define tl tuple<ll, ll, ll, ll>
#define tls tuple<ll, ll, ll>
#define INF numeric_limits<ll>::max()/2
#define MOD 1000000007
#define MIO 1000000
#define mp make_pair
#include <bits/stdc++.h>
using namespace std;
void hierholzer(int i, vector<vector<pii>>& adjlist, vector<vector<bool>>& active, vector<int>& output)
{
for(int k = 0; k < (int) adjlist[i].size(); k++)
{
if(active[i][k])
{
int j = adjlist[i][k].first;
int ind = adjlist[i][k].second;
active[i][k] = false;
active[j][ind] = false;
hierholzer(j, adjlist, active, output);
output.push_back(j);
}
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin>>n>>m;
vector<vector<pii>> adjlist(n, vector<pii> (0));
vector<vector<bool>> active(n, vector<bool> (0));
for(int i = 0; i < m; i++)
{
int a, b;
cin>>a>>b;
a--; b--;
adjlist[a].push_back({b, adjlist[b].size()});
adjlist[b].push_back({a, adjlist[a].size()-1});
}
for(int i = 0; i < n; i++)
{
active[i].assign(adjlist[i].size(), true);
}
vector<int> output(0);
hierholzer(0, adjlist, active, output);
output.push_back(0);
reverse(output.begin(), output.end());
/*for(int i : output)
{
cout<<i+1<<" ";
}
cout<<"\n";*/
stack<int> tour;
vector<bool> instack(n, false);
for(int i : output)
{
if(instack[i])
{
vector<int> senior(0);
int v = -1;
while(v != i)
{
v = tour.top();
tour.pop();
instack[v] = false;
senior.push_back(v);
}
tour.push(i);
instack[i] = true;
for(int j : senior)
{
cout<<j+1<<" ";
}
cout<<"\n";
}
else
{
tour.push(i);
instack[i] = true;
}
}
return 0;
}
