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

using namespace std;

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

void citire()
{
    freopen("biconex.in","r",stdin);
    freopen("biconex.out","w",stdout);
    scanf("%d %d\n",&n ,&m);
    for(int i=0; i<m; i++)
    {
        scanf("%d %d\n", & 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 minim=nivel[nod];
    int l=graf[nod].size();
    for (int i=0;i<l;i++)
    {
        int fiu=graf[nod][i];
        if (fiu==tata)
            continue;
        if (nivel[fiu])
        {
            minim=min(minim, nivel[fiu]);
            continue;
        }
        int x=top;
        int niv=rezolva(fiu, nod);
        if (niv>=nivel[nod])
        {
            vector <int> comp;
            comp.push_back(nod);
            while(top!=x)
            {
                comp.push_back(stiva[top]);
                top--;
            }
            sol.push_back(comp);
        }
        minim=min(niv, minim);
    }

    return minim;
}

void afisare()
{
    int lg=sol.size();
    for(int i=0; i<lg; i++)
    {
        int k=sol[i].size();
        for(int j=0; j<k; j++)
            printf("%d ", sol[i][j]);
        printf("\n");
    }

}

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