// header file
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
// pragma
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
// macros
#define endl "\n"
#define ll long long
#define mp make_pair
#define ins insert
#define lb lower_bound
#define pb push_back
#define ub upper_bound
#define lll __int128
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_multiset;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
vector<vector<int>> ans;
const int lim = 5e5 + 5;
vector<int> edges[lim], st;
priority_queue<int> del[lim];
bool active[lim];
int find_cycle(int nd) {
active[nd] = 1;
// cerr << "FIND CYCLE " << nd << endl;
while (edges[nd].size()) {
if(del[nd].size() && del[nd].top() == edges[nd].back()) {
edges[nd].pop_back();
del[nd].pop();
continue;
}
int cur = edges[nd].back();
edges[nd].pop_back();
del[cur].push(nd);
st.pb(nd);
if(active[cur]) {
// cerr << "FOUND CYCLE " << nd << " " << cur << endl;
// found cycle
active[nd] = 0;
return cur;
}
else {
// cerr << "MOVE " << nd << " " << cur << endl;
int x = find_cycle(cur);
// cerr << "RESULT " << nd << " " << cur << " " << x << endl;
if(x != nd) {
active[nd] = 0;
return x;
}
else {
ans.pb({});
do {
ans.back().pb(st.back());
st.pop_back();
} while(ans.back().back() != nd);
}
}
}
active[nd] = 0;
return -1;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(NULL);
int n, m;
cin >> n >> m;
for(int i = 1; i <= m; ++i) {
int u, v;
cin >> u >> v;
edges[u].pb(v);
edges[v].pb(u);
}
for(int i = 1; i <= n; ++i)
sort(edges[i].begin(), edges[i].end());
for(int i = 1; i <= n; ++i) {
if(edges[i].size())
find_cycle(i);
}
for(auto x : ans) {
for(auto y : x)
cout << y << " ";
cout << endl;
}
return 0;
}
