#include <bits/stdc++.h>
#define nikah ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ll long long
#define pll pair<ll,ll>
#define pb push_back
#define fi first
#define se second
const ll maxn = 5e5+7, modn = 1e9+7;
using namespace std;
ll n,m,cur,tim;
vector<pll>adj[maxn];
vector<ll>ans[maxn];
pll par[maxn];
ll par2[maxn], cnt[maxn];
bool cek[maxn];
void dfs(ll node, ll last) {
for (auto [next, idx] : adj[node]) {
if (par[next].se < last) par[next].fi = 0;
if (cek[idx] || next == par[node].fi) continue;
tim++;
if (par[next].fi == 0) {
par[next].fi = node;
par[next].se = tim;
par2[next] = idx;
dfs(next, last);
} else {
cur++;
ans[cur].pb(next);
cnt[next] -= 2;
cek[idx] = 1;
ll x = node;
// cout<<next<<" ";
while (x != next) {
// cout<<x<<" ";
cek[par2[x]] = 1;
ans[cur].pb(x);
cnt[x] -= 2;
x = par[x].fi;
}
// cout<<endl;
}
break;
}
}
int main () {
nikah
cin>>n>>m;
for (ll i=1; i<=m; i++) {
ll u,v; cin>>u>>v;
adj[u].pb({v,i});
adj[v].pb({u,i});
cnt[u]++;
cnt[v]++;
}
for (ll i=1; i<=n; i++) {
while (cnt[i] > 0) {
par[i].fi = -1;
par[i].se = tim;
dfs(i,tim);
}
}
for (ll i=1; i<=cur; i++) {
for (auto x : ans[i]) {
cout<<x<<" ";
}
cout<<endl;
}
}
