#include <fstream>
#include <cstdlib>
#include <vector>
#include <algorithm>
#include <stack>

using namespace std;

const static int nmax = 100001;

vector <int> graf[nmax];
vector <int> transpus[nmax];
vector <int> ctc[nmax];
stack<int> stiva;
bool sel[nmax];
int n , m;
int nrctc = 0;

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

void DF_Graf(int nod)
{
    sel[nod] = true;
    for (int i =0;i<graf[nod].size();i++)
    {
        if (!sel[graf[nod][i]]) DF_Graf(graf[nod][i]);
    }
    stiva.push(nod);
}

void DF_Transpus(int nod)
{
    sel[nod] = true;
    ctc[nrctc].push_back(nod);
    for (int i =0;i<transpus[nod].size();i++)
    {
        if (!sel[transpus[nod][i]]) DF_Transpus(transpus[nod][i]);
    }
}

int main()
{

    in >> n >> m;
    for (int i =0;i<m;i++)
    {
        int x , y;
        in >> x >> y;
        graf[x].push_back(y);
        transpus[y].push_back(x);
    }

    fill(sel,sel+n+1,false);

    for (int i =1;i<=n;i++)
    {
        if (!sel[i])
        {
            DF_Graf(i);
        }
    }

    fill(sel ,sel+n+1,0);

    while (!stiva.empty())
    {
        int nod = stiva.top();
        stiva.pop();
        if (!sel[nod])
        {
            DF_Transpus(nod);
            nrctc++;
        }
    }

    out << nrctc;

    for (int i =0;i<nrctc;i++)
    {
        out << "\n";
        for (int j =0;j<ctc[i].size();j++)
        {
            out << ctc[i][j] << " ";
        }
    }

    in.close();
    out.close();


    return 0;
}