#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
const int MOD = 1e9+7;
#define f first
#define s second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
void FASTIO() {ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); }
const int mxn = 5e5+5;
int n, m;
bool available[mxn];
vector<pii> adj[mxn];
bool in_stack[mxn];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for(int i = 0; i < m; i++) {
int a, b; cin >> a >> b;
available[i] = true;
adj[a].pb({b, i});
adj[b].pb({a, i});
}
vector<vi> ans;
stack<int> st;
for(int i = 1; i <= n; i++) {
while(!adj[i].empty() && !available[adj[i].back().s]) adj[i].pop_back();
if(adj[i].empty()) continue;
st.push(i);
in_stack[i] = true;
while(!st.empty()) {
int a = st.top();
while(!adj[a].empty() && !available[adj[a].back().s]) adj[a].pop_back();
int b = adj[a].back().f;
available[adj[a].back().s] = false;
adj[a].pop_back();
if(in_stack[b]) {
vi route;
while(st.top() != b) in_stack[st.top()] = false, route.pb(st.top()), st.pop();
while(!adj[b].empty() && !available[adj[b].back().s]) adj[b].pop_back();
if(adj[b].empty()) {
in_stack[b] = false;
st.pop();
}
route.pb(b);
ans.pb(route);
}
else {
in_stack[b] = true;
st.push(b);
}
}
}
for(auto v : ans) {
for(int a : v) {
cout << a << " ";
}
cout << "\n";
}
return 0;
}
/*
*/
