#include <bits/stdc++.h>
using namespace std;
#define MAXN 500001
int n,m;
vector<pair<int,int>> adj[MAXN];
vector<int> path;bool pos[MAXN];
vector<int> ans[MAXN];
stack<int> nodes;
int pojavljivanje[MAXN];
void dfs(int node)
{
while (!adj[node].empty())
{
pair<int,int> par=adj[node].back();adj[node].pop_back();
if (pos[par.second]) continue;
pos[par.second]=true;dfs(par.first);
}
path.push_back(node);
}
int main()
{
cin>>n>>m;
for (int i=1;i<=m;i++) {int x,y;cin>>x>>y;adj[x].push_back({y,i});adj[y].push_back({x,i});}
dfs(1);int trenkomp=0;
for (int pos=1;pos<=path.size();pos++)
{
int node=path[pos-1];if (pojavljivanje[node]==0) {pojavljivanje[node]=pos;nodes.push(node);continue;}
ans[trenkomp].push_back(node);
while (nodes.top()!=node) {ans[trenkomp].push_back(nodes.top());pojavljivanje[nodes.top()]=0;nodes.pop();}
nodes.pop();trenkomp++;pojavljivanje[node]=pos;nodes.push(node);
}
for (int komp=0;komp<trenkomp;komp++)
{
for (int node:ans[komp]) cout<<node<<" ";
cout<<endl;
}
}
