//#define _GLIBCXX_DEBUG
//#define _GLIBCXX_DEBUG_PEDANTIC
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
struct edge {
int vertex;
std::list<edge>::iterator opposite;
edge(int vertex, std::list<edge>::iterator opposite) : vertex(vertex), opposite(opposite) {};
edge(int vertex) : vertex(vertex) {};
};
int main() {
// std::ios_base::sync_with_stdio(false);
// std::cin.tie(nullptr);
int nvertex, nedge;
std::cin >> nvertex >> nedge;
std::vector<std::list<edge>> adjlist (nvertex);
for (int i = 0; i < nedge; ++i) {
int u, v;
std::cin >> u >> v;
adjlist[--u].emplace_front(--v);
adjlist[v].emplace_front(u);
adjlist[u].front().opposite = adjlist[v].begin(); // begin = iterator of front
adjlist[v].front().opposite = adjlist[u].begin(); // begin = iterator of front
}
// std::cout << "------------\n";
std::vector<int> passedvertices;
std::vector<char> passedp (nvertex, false);
for (int vertex = 0; vertex < nvertex; ++vertex) {
// std::cout << "vertex = " << vertex << '\n';
while (!adjlist[vertex].empty()) {
passedvertices.push_back(vertex);
passedp[vertex] = true;
while ((!passedvertices.empty()) && !adjlist[passedvertices.back()].empty()) {
edge e = adjlist[passedvertices.back()].back();
int nextvertex = e.vertex;
adjlist[nextvertex].erase(e.opposite);
adjlist[passedvertices.back()].pop_back(); // erase (e)
if (passedp[nextvertex]) {
// std::cout << "Cycle :\n";
do {
std::cout << 1+passedvertices.back() << ' ';
passedp[passedvertices.back()] = false; passedvertices.pop_back();
} while (passedvertices.back() != nextvertex);
std::cout << 1+nextvertex << '\n';
} else {
passedvertices.push_back(nextvertex);
passedp[nextvertex] = true;
}
}
}
}
}
