#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define debug(x) cerr << #x << " " << x << "\n"
#define debugs(x) cerr << #x << " " << x << " "
using namespace std;
typedef pair <int, int> pii;
typedef long long ll;
const int NMAX = 500001;
const int VMAX = 41;
const int INF = 1e9;
const int MOD = 1000000009;
const int BLOCK = 318;
const int base = 31;
const int nrbits = 21;
struct muchie {
int ambele;
int viz;
} edges[NMAX];
vector <int> v[NMAX];
vector <int> euler;
void DFS(int node) {
while(v[node].size()) {
int ind = v[node].back();
v[node].pop_back();
if(edges[ind].viz == 1) continue;
edges[ind].viz = 1;
int vecin = (edges[ind].ambele ^ node);
DFS(vecin);
}
euler.push_back(node);
}
vector <int> stiva;
int f[NMAX];
int main() {
#ifdef HOME
ifstream cin(".in");
ofstream cout(".out");
#endif // HOME
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, m, i;
cin >> n >> m;
for(i = 1; i <= m; i++) {
int x, y;
cin >> x >> y;
edges[i].ambele = (x ^ y);
edges[i].viz = 0;
v[x].push_back(i);
v[y].push_back(i);
}
DFS(1);
for(auto x : euler) {
debug(x);
if(f[x]) {
while(stiva.back() != x) {
cout << stiva.back() << " ";
f[stiva.back()]--;
stiva.pop_back();
}
cout << stiva.back() << " ";
f[stiva.back()]--;
stiva.pop_back();
cout << "\n";
}
stiva.push_back(x);
f[x]++;
}
return 0;
}
