#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <ctime>
#include <bitset>
#include <complex>
#include <chrono>
#include <random>
#include <functional>
using namespace std;
const int N = 5e5 + 7;
struct Edge {
int u, v;
int alive;
Edge() {}
Edge(int u_, int v_) {
u = u_;
v = v_;
alive = 1;
}
};
int in[N];
int et[N];
Edge ed[N];
vector<int> g[N];
int P = 0;
void dfs(int cur) {
while (!g[cur].empty()) {
if (ed[g[cur].back()].alive) {
ed[g[cur].back()].alive = 0;
int v = ed[g[cur].back()].u;
if (v == cur) {
v = ed[g[cur].back()].v;
}
dfs(v);
} else {
g[cur].pop_back();
}
}
et[P] = cur;
P++;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
for (int i = 0; i < m; i++) {
cin >> ed[i].u >> ed[i].v;
ed[i].alive = 1;
ed[i].u--;
ed[i].v--;
g[ed[i].u].push_back(i);
g[ed[i].v].push_back(i);
}
dfs(0);
vector<int> st;
for (int i = 0; i < P; i++) {
int t = et[i];
if (in[t] > 0) {
while (true) {
int br = (st.back() == t);
in[st.back()]--;
cout << st.back() + 1 << ' ';
st.pop_back();
if (br) break;
}
cout << '\n';
}
in[t]++;
st.push_back(t);
}
}
