#include<bits/stdc++.h>
using namespace std;
#define fori(i, a, b) for(int i = (int) (a); i <= (int) (b); i++)
#define ford(i, a, b) for(int i = (int) (b); i >= (int) (a); i--)
#define ii pair<int, int>
#define fi first
#define se second
#define vi vector<int>
#define eb emplace_back
#define sp ' '
#define endl '\n'
#define int long long
const int maxn = 5e5 + 5;
int n, m;
multiset<int> g[maxn];
vector<int> ans;
void dfs(int);
vector<vi> decompose();
bool vs[maxn];
void dfs(int u) {
while(g[u].size()) {
int v = *begin(g[u]);
g[u].erase(g[u].find(v));
g[v].erase(g[v].find(u));
dfs(v);
}
ans.eb(u);
// cout << u << endl;
}
vector<vi> decompose() {
stack<int> cur;
vector<vi> re;
for(int u: ans) {
if(!vs[u]) {
cur.push(u);
vs[u] = 1;
}
else {
vi cyc;
while(vs[u]) {
cyc.eb(cur.top());
vs[cur.top()] = 0;
cur.pop();
}
re.eb(cyc);
cur.push(u);
vs[u] = 1;
}
}
return re;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
fori(i, 1, m) {
int u, v; cin >> u >> v;
g[u].insert(v);
g[v].insert(u);
}
dfs(1); // since the thing is connected
auto t = decompose();
for(auto cyc: t) {
for(int u: cyc) {
cout << u << sp;
}
cout << endl;
}
}
