#include <iostream>
#include <vector>
#include <set>
struct Road
{
int a,b;
bool visit;
bool full_visit;
};
struct Node
{
std::set<int> roads;
};
int main()
{
int N,M;
std::cin >> N >> M;
std::vector<Node> nodes(N+1);
std::vector<Road> roads(M);
for(auto& i : roads)
{
std::cin >> i.a >> i.b;
nodes[i.a].roads.insert(&i-roads.data());
nodes[i.b].roads.insert(&i-roads.data());
}
std::vector<std::vector<int>> os;
int s = 1;
while(s <= N)
{
auto& out = os.emplace_back();
while(s <= N && nodes[s].roads.size()==0) s++;
if(s>N) break;
out.push_back(s);
while(out.size()==1||out.back()!=out.front())
{
auto r = *nodes[out.back()].roads.begin();
auto n = roads[r].a==out.back()?roads[r].b:roads[r].a;
nodes[n].roads.erase(r);
nodes[out.back()].roads.erase(r);
out.push_back(n);
}
}
std::vector<std::vector<int>> res;
for(auto v : os)
{
std::set<int> seen;
std::vector<int> out;
for(auto i : v)
{
if(seen.count(i))
{
auto& w = res.emplace_back();
w.push_back(i);
while(out.back()!=i)
{
w.push_back(out.back());
seen.erase(out.back());
out.pop_back();
}
}
else
{
seen.insert(i);
out.push_back(i);
}
}
}
for(auto v : res)
{
for(auto i : v) std::cout << i << " ";
std::cout << "\n";
}
}
