#include <fstream>
#include <vector>
#include <algorithm>
#include <stack>
#define INF 0x3f3f3f3f
using namespace std;

ifstream is("biconex.in");
ofstream os("biconex.out");

using VI = vector<int>;
using VVI = vector<VI>;

int n, m;
VI nv, nm, t, c;
VVI g, answ;
stack<pair<int, int>> s;

void Read();
void CB(int nod, int niv);
void Write();
void Make(int x, int y);

int main()
{
    Read();
    nv = nm = t = VI(n + 1);
    for ( int i = 1; i <= n; ++i )
        if ( !nv[i] )
        {
            CB(i, 1);
            t[i] = i;
        }
    Write();
    is.close();
    os.close();
    return 0;
}

void CB(int nod, int niv)
{
    nv[nod] = nm[nod] = niv;
    for ( const auto &nodv : g[nod] )
    {
        if ( t[nod] == nodv )
            continue;
        if ( !nv[nodv] )
        {
            t[nodv] = nod;
            s.push(make_pair(nod, nodv));
            CB(nodv, niv + 1);
            if ( nm[nodv] > nm[nod] )
                Make(nod, nodv);
        }
        else
            nm[nod] = min(nm[nod], nv[nodv]);
    }
}

void Make(int x, int y)
{
    c.clear();
    while ( true )
    {
        c.push_back(s.top().first);
        c.push_back(s.top().second);
        if ( x == s.top().first && y == s.top().second )
            break;
        s.pop();
    }
    s.pop();
    sort(c.begin(), c.end());
    c.erase(unique(c.begin(), c.end()), c.end());
    answ.push_back(c);
}

void Write()
{
    os << answ.size() << "\n";
    for ( const auto i : answ )
    {
        for ( const auto j : i )
            os << j << " ";
        os << "\n";
    }
}

void Read()
{
    is >> n >> m;
    g = VVI(n + 1);
    int x, y;
    for ( int i = 1; i <= n; ++i )
    {
        is >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
}