#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 5;
vector<pair<int, int>> adj[N];
vector<int> vis(N, 0);
vector<int> lst(N, - 1);
vector<int> path;
void dfs(int u) {
while (!adj[u].empty()) {
auto [v, i] = adj[u].back();
adj[u].pop_back();
if (vis[i]) continue;
vis[i] = 1;
dfs(v);
}
path.push_back(u);
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
adj[a].push_back({b, i});
adj[b].push_back({a, i});
}
dfs(1);
reverse(path.begin(), path.end());
vector<int> cur;
for (int i = 0; i < (int)path.size(); i++) {
if (lst[path[i]] == - 1) {
cur.push_back(path[i]);
lst[path[i]] = 1;
} else {
vector<int> op;
while (cur.back() != path[i]) {
op.push_back(cur.back());
lst[cur.back()] = - 1;
cur.pop_back();
}
op.push_back(path[i]);
reverse(op.begin(), op.end());
for (int &j: op) {
cout << j << ' ';
}
cout << '\n';
}
}
return 0;
}
