#include <bits/stdc++.h>
#define maxn 100000
#define maxm 200000

using namespace std;

vector <int> g[maxn+5];
map <pair<int,int>,bool> hh;
map <pair<int,int>,bool> mart;
vector < pair<int,int> > muc;
bool viz[maxn+5];
int dad[maxn+5]; /// tata nod
bool art[maxn+5]; /// pct de articulatie
int low[maxn+5];
int niv[maxn+5];

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

int print ( int i, int m )
{
  bool v[m+1];
  int flag = 0, a, b;
  while ( i >= 0 && flag == 0 )
  {
    a = muc[i].first;
    b = muc[i].second;
    if ( mart[{a,b}] == 1 )
      flag = 1;
    if ( v[a] == 0 )
      fout << a + 1 << ' ';
    if ( v[b] == 0 )
      fout << b + 1 << ' ';
    v[a] = v[b] = 1;
    i--;
  }
  return i;
}

void add_edgehh ( int a, int b )
{
  if ( a > b )
    swap ( a, b );
  hh[{a,b}] = 1;
  hh[{b,a}] = 1;
  muc.push_back ( make_pair ( a, b ) );
}

void dfs ( int tata, int nod )
{
  int i, sz = g[nod].size (), nn;

  dad[nod] = tata;
  viz[nod] = 1;
  if ( tata != -1 )
    niv[nod] = 1 + niv[tata];
  low[nod] = niv[nod];

  int oth_low = INT_MAX;

  for ( i = 0; i < sz; i++ )
  {
    nn = g[nod][i];
    if ( !viz[nn] )
    {
      add_edgehh ( nod, nn );
      dfs ( nod, nn );
      oth_low = min ( oth_low, low[nn] );
    }
    else if ( nn != tata ) /// back edge
      low[nod] = low[nn];
  }

  low[nod] = min ( low[nod], oth_low );
}

int main ()
{
  int n, m;

  fin >> n >> m;

  int i, j, x, y, sz;

  for ( i = 0; i < m; i++ )
  {
    fin >> x >> y;
    g[x-1].push_back ( y - 1 );
    g[y-1].push_back ( x - 1 );
  }

  for ( i = 0; i < n; i++ )
    if ( !viz[i] )
    {
      niv[i] = 1;
      dfs ( -1, i );
    }

  for ( i = 0; i < n; i++ )
  {
    if ( dad[i] == -1 && g[i].size () > 2 )
      art[i] = 1;
    else if ( dad[i] != -1 && low[i] >= niv[dad[i]] )
      art[dad[i]] = 1;
  }

  int a, b, pa = 0;
  for ( i = 0; i < n; i++ )
    if ( art[i] == 1 )
    {
      sz = g[i].size ();
      for ( j = 0; j < sz; j++ )
        if ( ( hh[{i,g[i][j]}] == 1 || hh[{g[i][j],i}] == 1 ) && dad[i] != g[i][j] )
        {
          pa++;
          a = min ( i, g[i][j] ); b = max ( i, g[i][j] );
          mart[{a,b}] = 1;
          hh[{i,g[i][j]}] = hh[{g[i][j],i}] = 0;
        }
    }

  fout << pa << '\n';

  int nmu = muc.size ();
  i = nmu - 1;
  while ( i >= 0 )
  {
    i = print ( i, nmu );
    fout << '\n';
  }

  fin.close ();
  fout.close ();

  return 0;
}