#include <bits/stdc++.h>
using namespace std;
int main() {
int n, m, x, y;
cin >> n >> m;
vector<vector<pair<int, int>>> G(n + 1);
vector<int> seen(m);
for (int i = 0; i < m; ++i) {
cin >> x >> y;
G[x].emplace_back(y, i);
G[y].emplace_back(x, i);
}
vector<int> ans, cur;
cur.reserve(n + 1);
cur.emplace_back(1);
while (!cur.empty()) {
int top = cur.back();
if (G[top].empty()) {
ans.emplace_back(top);
cur.back();
}
else {
if (seen[G[top].back().second]) {
G[top].pop_back();
continue;
}
auto [node, e] = G[top].back();
cur.emplace_back(node);
seen[e] = 1;
G[top].pop_back();
}
}
seen.assign(n + 1, 0);
for (auto x : ans)
if (!seen[x]) {
seen[x] = 1;
cur.emplace_back(x);
}
else {
cout << x << ' ';
while (cur.back() != x) {
cout << cur.back() << ' ';
seen[cur.back()] = 0;
cur.pop_back();
}
cout << '\n';
}
}
