#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define fr first
#define sc second
#define bg begin()
#define ed end()
#define lf(no) no << 1
#define rg(no) lf(no) | 1
#define lsb(x) x & (-x)
#define all(x) x.begin(),x.end()
#define sz(x) (int) x.size()
#define debug(x) cout << x << endl;
using namespace std;
using pii = pair<int,int>;
using tii = tuple<int,int,int>;
const int maxn = 5e5 + 10;
int n,m,t,qtd[maxn],mark[maxn],mv[maxn];
vector<int> resp[maxn],id[maxn];
stack<int> p;
pii e[maxn];
void find(int u){
if(mv[u]){
t++;
int v;
do{
v = p.top();
p.pop();
mv[v] = 0;
resp[t].pb(v);
}while(v != u);
}
mv[u] = 1;
while(sz(id[u])){
int ind = id[u].back();
if(mark[ind]){
id[u].pop_back();
continue;
}
mark[ind] = 1;
int v = e[ind].fr + e[ind].sc - u;
id[u].pop_back();
p.push(u);
find(v);
}
}
void solve(){
cin >> n >> m;
for(int i = 1;i <= m;i++){
int u,v;
cin >> u >> v;
e[i] = {u,v};
id[u].pb(i);
id[v].pb(i);
}
find(1);
for(int i = 1;i <= t;i++){
for(int v : resp[i])
cout << v << " ";
cout << "\n";
}
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t = 1;
//cin >> t;
while(t--)
solve();
return 0;
}
