#include "bits/stdc++.h"
#define ld double
#define ll long long
#define ull unsigned long long
#define llinf 100000000000000000LL // 10^17
#define iinf 2000000000 // 2*10^9
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) int(a.size())
#define all(a) a.begin(),a.end()
#define rall(a) a.begin(),a.end(),greater<int>()
#define here cerr<<"---------------------------\n"
#define ceri(a,l,r) {for(ll i = l;i<=r;i++) cerr<<a[i]<< " ";cerr<<endl;}
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl
using namespace std;
#define maxn 500005
vector<pll> g[maxn];
ll n,m;
bool vis[maxn];
vector<ll> ans;
ll it[maxn];
bool vis2[maxn];
void euler(ll u){
vis2[u] = 1;
ans.pb(u);
while(it[u]<sz(g[u])){
pll p = g[u][it[u]];
ll s = p.fi;
ll j = p.sc;
it[u]++;
if(vis[j]) continue;
vis[j] =1;
euler(s);
}
}
void tc(){
ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
cin >> n >> m;
for(ll i = 1;i<=m;i++){
ll x,y; cin >> x >> y;
g[x].pb({y,i});
g[y].pb({x,i});
}
for(ll i = 1;i<=n;i++) if(!vis2[i]) euler(i);
fill(vis,vis+maxn,0);
vector<ll> v;
vector<ll> w;
for(ll x : ans){
if(vis[x]==1){
while(v.back()!=x){
w.pb(v.back());
v.popb();
}
w.pb(x);
for(ll y : w){
vis[y] = 0;
cout<<y<< " ";
}
cout<<endl;
w.clear();
vis[x] = 1;
}else vis[x] = 1,v.pb(x);
}
}
int main(){
ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
int t; t = 1;
while(t--){
tc();
}
return 0;
}
