#include <bits/stdc++.h>
#define ll int
#define fr(i, d, c) for(ll i = d; i <= c; i++)
#define fl(i, d, c) for(ll i = d; i >= c; i--)
const int N = 5e5 + 9;
using namespace std;
ll n, m;
bool dd[N], xoa[N];
vector<pair<ll, ll>> adj[N];
stack<ll> st;
void clear_back(vector<pair<ll, ll>> & x) {
while(x.size() && xoa[x.back().second]) x.pop_back();
}
void run(ll u, ll bd) {
dd[u] = true;
st.push(u);
clear_back(adj[u]);
auto [v, id] = adj[u].back();
xoa[id] = true;
if(dd[v] == true) {
while(true) {
ll t = st.top();
st.pop();
cout<<t<<" ";
dd[t] = false;
if(t == v) break;
}
cout<<'\n';
}
if(v != bd) run(v, bd);
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
fr(i, 1, m) {
ll x, y;
cin>> x >> y;
adj[x].push_back({y, i});
adj[y].push_back({x, i});
}
fr(i, 1, n) {
clear_back(adj[i]);
while(adj[i].size()) {
run(i, i);
clear_back(adj[i]);
}
}
}
