#include <bits/stdc++.h>
using namespace std;
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
int N, M;
cin >> N >> M;
vector<vector<pair<int, int>>> G(N);
for (int i = 0; i < M; i++) {
int u, v;
cin >> u >> v;
u--, v--;
G[u].push_back({v, i});
G[v].push_back({u, i});
}
vector<int> ptr(N);
vector<bool> used(M);
vector<int> path;
stack<int> s;
s.push(0);
while (!s.empty()) {
int u = s.top();
while (ptr[u] < (int)G[u].size() && used[G[u][ptr[u]].second]) {
ptr[u]++;
}
if (ptr[u] == (int)G[u].size()) {
path.push_back(u);
s.pop();
} else {
used[G[u][ptr[u]].second] = true;
s.push(G[u][ptr[u]++].first);
}
}
vector<bool> occ(N, false);
vector<vector<int>> cycles;
vector<int> b;
for (int v : path) {
b.push_back(v);
if (occ[v]) {
cycles.push_back({});
cycles.back().push_back(v);
b.pop_back();
while (b.back() != v) {
cycles.back().push_back(b.back());
occ[b.back()] = false;
b.pop_back();
}
} else {
occ[v] = true;
}
}
for (auto cycle : cycles) {
int k = (int)cycle.size();
for (int i = 0; i < k; i++) {
cout << 1 + cycle[i] << " \n"[i + 1 == k];
}
}
}
