#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define PI acos(-1)
#define LSB(i) ((i) & -(i))
#define ll long long
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define sc second
#define th third
#define fo fourth
#define pii pair<int,int>
#define pll pair<ll,ll>
#define ldb double
#define INF 1e15
#define MOD 1000000007
#define endl "\n"
#define all(data) data.begin(),data.end()
#define TYPEMAX(type) std::numeric_limits<type>::max()
#define TYPEMIN(type) std::numeric_limits<type>::min()
#define MAXN 500007
vector<pll> adj[MAXN];
vector<ll> et;
bool vis[MAXN],vise[MAXN];
ll lst[MAXN];
void DFS(ll u)
{
vis[u]=true;
while(!adj[u].empty())
{
pll vw=adj[u].back(); adj[u].pop_back();
ll v=vw.fi,w=vw.sc;
if(vise[w]) continue;
vise[w]=true; DFS(v);
}
et.pb(u);
}
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
ll n,m,u,v; cin>>n>>m;
for(int i=1;i<=m;i++)
{
cin>>u>>v;
adj[u].pb({v,i}); adj[v].pb({u,i});
}
for(int i=1;i<=n;i++)
{
if(!vis[i]) DFS(i);
}
for(int i=1;i<=n;i++) lst[i]=-1;
stack<ll> st;
for(int i=0;i<et.size();i++)
{
ll u=et[i];
if(lst[u]==-1) {lst[u]=i; st.push(u);}
else
{
cout<<u<<" ";
while(lst[st.top()]>lst[u]) {cout<<st.top()<<" "; lst[st.top()]=-1; st.pop();}
cout<<endl;
}
}
return 0;
}
