#include<bits/stdc++.h>
using namespace std;
/*for ordered_set
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree<pair<int,int>, null_type,less<pair<int,int>>, rb_tree_tag,tree_order_statistics_node_update>
*/
const long long INFll = (long long) 1e18 + 10;
const int INFii = (int) 1e9 + 10;
typedef long long ll;
typedef int ii;
typedef long double dbl;
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define maxn 550000
ii n, m, blk[maxn], nx[maxn], mark[maxn];
vector<pair<ii,ii>> g[maxn];
void dfs(ii u) {
if(mark[u]) {
ii v = u;
cout << v << " ";
mark[v] = 0;
v = nx[v];
while(v != u) {
cout << v << " ";
mark[v] = 0;
v = nx[v];
}
cout << endl;
}
mark[u] = 1;
while(g[u].size()) {
ii v = g[u].back().fr;
ii id = g[u].back().sc;
g[u].pop_back();
if(blk[id]) continue;
blk[id] = 1;
nx[u] = v;
mark[u] = 1;
// cout << u << " -> " << v << endl;
dfs(v);
}
}
void solve() {
cin >> n >> m;
for(ii i = 1; i <= m; i++) {
ii u, v; cin >> u >> v;
g[u].pb(mp(v,i));
g[v].pb(mp(u,i));
}
// for(ii i = 1; i <= n; i++) reverse(all(g[i]));
dfs(1);
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
// freopen("in.in", "r", stdin);
//freopen("out.out", "w", stdout);
ii tt = 1;
// cin >> tt;
while(tt--) solve();
}
