#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MXN = 5e5 + 5;
int n, m;
vector<array<int, 2>> adj[MXN];
int used[MXN];
vector<int> o;
void dfs(int a) {
while (!adj[a].empty()) {
auto [v, id] = adj[a].back();
adj[a].pop_back();
if (used[id]) continue;
used[id] = 1;
dfs(v);
}
o.push_back(a);
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= m; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back({v, i});
adj[v].push_back({u, i});
}
dfs(1);
fill(used + 1, used + n + 1, 0);
vector<int> cur;
for (int &i : o) {
if (used[i]) {
while (used[i]) {
cout << cur.back() << ' ';
used[cur.back()] = 0;
cur.pop_back();
}
cout << '\n';
}
used[i] = 1;
cur.push_back(i);
}
}
