#include <bits/stdc++.h>
#define imie(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
using namespace std;
typedef long long ll;
typedef long double ld;
const int MOD = 1000000007;
const int MAXN = 5e5 + 5;
vector<pair<int, int>> graf[MAXN];
vector<int> sciezka;
vector<bool> visited(MAXN, false);
vector<bool> b(MAXN, false);
void dfs(int v) {
while(!graf[v].empty()) {
pair<int, int> p = graf[v].back();
int w = p.first;
int ind = p.second;
graf[v].pop_back();
if(!visited[ind]) {
visited[ind] = true;
dfs(w);
}
}
sciezka.push_back(v);
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
int n, m;
cin >> n >> m;
for(int i = 0; i < m; i++) {
int a,b;
cin >> a >> b;
graf[a].push_back({b,i});
graf[b].push_back({a,i});
}
dfs(1);
vector<int> v;
reverse(sciezka.begin(), sciezka.end());
for(auto &s : sciezka) {
if(b[s]) {
cout << s << ' ';
while(v.back() != s) {
b[v.back()] = 0;
cout << v.back() << ' ';
v.pop_back();
}
cout << '\n';
} else {
b[s] = 1;
v.push_back(s);
}
}
return 0;
}
