#include <fstream>
#include <vector>

using namespace std;

ifstream fin ("biconex.in");
ofstream fout ("biconex.out");

void YNY ();
void RF ();

unsigned int N, M;
unsigned int x, y;

vector <unsigned int> G[100001];
unsigned int matrix[10001][10001], matrix1[10001][10001], matrix0[10001][10001];
unsigned int i, j, k, cnt, cnt0, w, q;
int xx[100001];

unsigned int sol;

int main ()
{
    fin >> N >> M;
    for (i=1; i<=M; i++)
    {
        fin >> x >> y;
        matrix[x][y] = 1;
        matrix[y][x] = 1;
    }
    for (i=1; i<=N; i++)
        for (j=1; j<=N; j++)
            matrix0[i][j] = matrix[i][j];
    for (k=1; k<=N; k++)
        for (i=1; i<=N; i++)
            for (j=1; j<=N; j++)
                if (i!=j && matrix0[i][k]!=0 && matrix0[k][j]!=0 && (matrix0[i][j]>matrix0[i][k]+matrix0[k][j] || matrix0[i][j]==0))
                    matrix0[i][j] = matrix0[i][k] + matrix0[k][j];
    for (i=1; i<=N; i++)
        for (j=1; j<=N; j++)
            if (matrix0[i][j] > 0)
                cnt0++;
    cnt0 /= 2;
    for (i=1; i<=N; i++)
    {
        YNY();
        for (j=1; j<=N; j++)
        {
            matrix1[i][j] = 0;
            matrix1[j][i] = 0;
        }
        RF();
        cnt = 0;
        for (j=1; j<=N; j++)
            for (k=1; k<=N; k++)
                if (matrix1[j][k] > 0)
                {
                    cnt++;
                    G[j].push_back(k);
                }
        cnt /= 2;
        if (cnt != cnt0)
        {
            sol++;
            xx[i] = i;
        }
    }
    sol /= 2;

    /// PRINT
    fout << sol << '\n';
    for (i=1; i<=sol; i++)
    {
        //fout << xx[i] << ' ';
        for (j=1; j<G[i].size(); j++)
            fout << G[i][j] << ' ';
        fout << '\n';
    }
    return 0;
}

void YNY ()
{
    int i, j;
    for (i=1; i<=N; i++)
        for (j=1; j<=N; j++)
            matrix1[i][j] = matrix[i][j];
}

void RF ()
{
    int i, j, k;
    for (k=1; k<=N; k++)
        for (i=1; i<=N; i++)
            for (j=1; j<=N; j++)
                if (i!=j && matrix1[i][k]!=0 && matrix1[k][j]!=0 && (matrix1[i][j]>matrix1[i][k]+matrix1[k][j] || matrix1[i][j]==0))
                    matrix1[i][j] = matrix1[i][k] + matrix1[k][j];
}