#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <cstring>
using namespace std;
ifstream f("biconex.in");
ofstream g("biconex.out");
int n,m,x,y,viz[100001],low[100001],ok[100001];
stack <pair<int,int>> st;
vector <vector <int>> v(100001),afis;
void validatecompconx (int a,int b)
{
    //cout<<a<<' '<<b<<'\n';
    vector <int> ins;
    int insi=st.top().first,insj=st.top().second;
    st.pop();ins.push_back(insi);
        ins.push_back(insj);
    while ((insi!=a || insj!=b))
    {
        insi=st.top().first;
        insj=st.top().second;
        st.pop();
        ins.push_back(insi);
        ins.push_back(insj);
    }
    /*int insi,insj;
    do
    {
        insi=st.top().first,insj=st.top().second;
        st.pop();
        ins.push_back(insi);
        ins.push_back(insj);
    }while (insi!=a || insj!=b);*/
    afis.push_back(ins);
}
void dfs (int cur,int previous,int nr)
{

    viz[cur]=low[cur]=nr;
    /*for (int i=1; i<=n; i++)
        cout<<viz[i]<<' ';
    cout<<'\n';*/
    for (int j=0; j<v[cur].size(); j++)
    {
        //cout<<cur<<' '<<j<<'\n';
        int next=v[cur][j];
        if (next!=previous)
        {
            //cout<<cur<<' '<<next<<' ';
            if (viz[next]==-1)
            {
               // cout<<1<<'\n';
                st.push(make_pair(cur,next));
                dfs(next,cur,nr+1);
                low[cur]=min(low[cur],low[next]);
                if (low[next]>=viz[cur])
                    validatecompconx(cur,next);
            }
            else
            {
                //cout<<2<<'\n';
                low[cur]=min(low[cur],viz[next]);
            }
        }
    }
}
int main()
{
    f>>n>>m;
    for (int i=1; i<=m; i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for (int i=1; i<=n; i++)
        viz[i]=-1;
    dfs(1,0,0);
    for (int i=0; i<afis.size(); i++)
    {
        memset(ok,0,sizeof(ok));
        for (int j=0; j<afis[i].size(); j++)
        {
            if (ok[afis[i][j]]==0)
            {
                ok[afis[i][j]]=1;
            g<<afis[i][j]<<' ';
            }
        }
        g<<'\n';
    }
    return 0;
}