#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef pair<long, long> pll;
typedef pair<double, double> pdd;
/*
desde quando vi da ultima vez até quando vejo de novo, deixo ele em ans sozinho
*/
const int MAXN = 5e5+10;
vector<pii> e[MAXN];
vector<int> ans;
bool ve[MAXN];
bool v[MAXN];
void dfs(int x){
while (!e[x].empty()){
pii u = e[x].back();
e[x].pop_back();
if (ve[u.second] == 1) continue;
ve[u.second] = 1;
dfs(u.first);
}
ans.push_back(x);
if (!v[x]) v[x] = 1;
else{
cout << x;
ans.pop_back();
while (ans.back() != x){
cout << " " << ans.back();
ans.pop_back();
}
cout << "\n";
}
}
int main(){
std::ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
int a, b;
for (int i=0;i<m;i++){
cin >> a >> b;
e[a].emplace_back(b, i);
e[b].emplace_back(a, i);
}
dfs(1);
}
