#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;

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

int  i, n, a, b, fv[100005], mi[100005], ctc, nr, m, j, scs[100005];

vector < int > gf[100005], rsp[100005];

stack < int > st;

int dfs ( int nod )
{
    nr++;
    fv[nod] = nr;
    mi[nod] = nr;

    st.push(nod);

    for ( int i = 0 ; i < gf[nod].size() ; i++ )
    {
        if ( fv [ gf[nod][i] ] == 0)
            dfs( gf[nod][i] );
        if ( scs[gf[nod][i]] == 0 )
            mi[nod] = min ( mi[nod], mi[ gf[nod][i] ] );
    }

    if ( mi[nod] == fv[nod] )
    {
        ctc++;
        while ( st.top() != nod )
        {
            scs[st.top()] = 1;
            rsp[ctc].push_back(st.top());
            st.pop();
        }
            scs[st.top()] = 1;
            rsp[ctc].push_back(st.top());
            st.pop();

    }

    return mi[nod];

}

int main ()
{
    fin>>n>>m;

    for ( i = 1; i <= m ; i++ )
    {
        fin>>a>>b;

        gf[a].push_back(b);

    }

    for ( i = 1; i <= n ; i++ )
    {
        nr = 0;
        if ( fv[i] == 0 )
            dfs(i);
    }

    fout<<ctc<<'\n';

    for ( i = 1 ; i <= ctc ; i++ )
    {
        for ( j = 0 ; j < rsp[i].size() ; j++ )
        {
            fout<<rsp[i][j]<<" ";
        }
        fout<<'\n';
    }

    return 0;
}