#include <iostream>
#include <cstdio>
#include <vector>
#include <fstream>
#define N 200005
#define min(a,b) a<b?a:b

using namespace std;

ifstream f("biconex.in");
ofstream g("biconex.out");

int n,m,a,b,top;
int stiva[N],nivel[N];
vector <int> graf[N];
vector <vector<int> > solutie;

void citire()
{

    f>>n>>m;
    for(int i=0; i<m; i++)
    {
        f>>a>>b;
        graf[a].push_back(b);
        graf[b].push_back(a);
    }
}

int rezolva(int nod, int tata)
{
    nivel[nod]=nivel[tata]+1;
    stiva[++top]=nod;
    int mini=nivel[nod];
    int l=graf[nod].size();
    for (int i=0;i<l;i++)
    {
        int copil=graf[nod][i];
        if (copil==tata)
            continue;
        if (nivel[copil])
        {
            mini=min(mini, nivel[copil]);
            continue;
        }
        int x=top;
        int niv=rezolva(copil, nod);
        if (niv>=nivel[nod])
        {
            vector <int> comp;
            comp.push_back(nod);
            while(top!=x)
            {
                comp.push_back(stiva[top]);
                top--;
            }
            solutie.push_back(comp);
        }
        mini=min(niv, mini);
    }

    return mini;
}

void afisare()
{
    int lg=solutie.size();

    for(int i=0; i<lg; i++)
    {
        int k=solutie[i].size();
        for(int j=0; j<k; j++)
             g<<solutie[i][j]<<" ";
        g<<'\n';
    }

}

int main()
{
    citire();
    rezolva(1,0);
    afisare();
    return 0;
}