#include <iostream>
#include <vector>
#include <cstdlib>
using namespace std;
const int mx = 500'000;
using vi = vector<int>;
using vvi = vector<vi>;
#define sz(x) int(x.size())
int N, M;
vi u(1+mx), v(1+mx);
vi edge[1+mx];
vi visit(1+mx, 0);
vi adj_ind(1+mx, 0);
vi instack(1+mx, 0);
vi st;
vvi res;
// int ct = 0;
void dfs(int x)
{
// if(++ct == 50) exit(0);
// cerr << "dfs " << x << '\n';
while(adj_ind[x] < sz(edge[x]) && visit[ edge[x][adj_ind[x]] ])
{
adj_ind[x]++;
// cerr << adj_ind[x] << '\n';
}
if(adj_ind[x] == sz(edge[x])) return;
int e = edge[x][adj_ind[x]];
// cerr << "edge = " << e << '\n';
int y = u[e] + v[e] - x;
visit[e] = 1;
// cerr << "visit : " << e << '\n';
if(instack[y])
{
res.push_back(vi(0));
while(1)
{
// cerr << "w\n";
res.back().push_back(st.back());
if(st.back() == y) break;
instack[st.back()] = 0;
st.pop_back();
}
// cerr << x << " -> " << y << '\n';
dfs(y);
// cerr << "done instack\n";
}
else
{
instack[y] = 1;
st.push_back(y);
dfs(y);
}
// cerr << "terminate dfs\n";
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> N >> M;
for(int e = 1; e <= M; e++)
{
cin >> u[e] >> v[e];
edge[u[e]].push_back(e);
edge[v[e]].push_back(e);
}
for(int e = 1; e <= M; e++)
{
while(!visit[e])
{
// cerr << "e = " << e << '\n';
st.push_back(u[e]);
instack[u[e]] = 1;
dfs(u[e]);
// cerr << "###\n";
// cerr << visit[e] << '\n';
instack[u[e]] = 0;
// cerr << "instack cleared\n";
// exit(0);
// st.clear();
// cerr << "st cleared\n";
// cerr << "while instance done\n";
}
// cerr << "e = " << e << " done \n";
}
for(vi& r: res)
{
for(int u: r)
cout << u << ' ';
cout << '\n';
}
}
