#include <iostream>
#include <vector>
using namespace std;
const int N = 1<<19;
vector<pair<int, int>> nei[N];
vector<int> pth, v;
int d[N], id[N], vis[N], seen[N];
void cycle(int u){
if (nei[u].size() == 0)
return;
while (id[u] < nei[u].size()){
auto [v, ind] = nei[u][id[u]++];
if (vis[ind])
continue;
vis[ind] = 1;
cycle(v);
pth.push_back(v);
}
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
int n, m, k = 0;
cin>>n>>m;
for (int i=1;i<=m;i++){
int a, b;
cin>>a>>b;
nei[a].push_back({b, i});
nei[b].push_back({a, i});
}
cycle(1);
pth.push_back(1);
for (int i : pth){
if (seen[i]){
cout<<i<<' ';
while (v.back() != i){
cout<<v.back()<<' ', seen[v.back()] = 0, v.pop_back();
}
cout<<endl;
}
else
v.push_back(i);
seen[i] = 1;
}
}
