#include <bits/stdc++.h>
#define N 500050
#define f first
#define s second
using namespace std;
typedef pair<int, int> pii;
int n, m, block[N], cnt = 0, usado[N], prox[N], id = 1;
vector<pii> grafo[N];
vector<int> path[N];
bool dfs(int x, int ini, int f)
{
//cout<<"DFS "<<x<<"\n";
usado[x] = id;
for(auto v: grafo[x])
{
if(v.f == ini and !block[v.s])
{
block[v.s] = 1;
// cout<<"PROX "<<x<<" "<<"-1\n";
prox[x] = -1;
return true;
}
if(usado[v.f] == id or block[v.s]) continue;
//cout<<"DFS "<<x<<" to "<<v.f<<"\n";
if(dfs(v.f, ini, f))
{
prox[x] = v.f;
// cout<<"PROX "<<x<<" "<<v.f<<"\n";
block[v.s] = 1;
return true;
}
}
return false;
}
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>m;
for(int i = 1, a, b; i <= m; i++)
{
cin>>a>>b;
grafo[a].push_back({b, i});
grafo[b].push_back({a, i});
}
for(int x = 1; x <= n; x++)
{
for(auto v: grafo[x])
{
if(block[v.s]) continue;
++id;
usado[x] = id;
block[v.s] = 1;
path[cnt].push_back(x);
if(dfs(v.f, x, cnt))
{
int u = v.f;
while(u != -1)
{
path[cnt].push_back(u);
u = prox[u];
}
++ cnt;
}
}
}
for(int i = 0; i < cnt; i++)
{
for(auto x: path[i]) cout<<x<<" ";
cout<<"\n";
}
}
