#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

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

int n, m, x, y, sol;
vector < int > direct[100005], invers[100005], ctc[100005], srt;
bitset < 100005 > viz;

vector<int>::iterator it;

void dfsDirect(int nod)
{
    viz[nod]=1;
    for (it=direct[nod].begin(); it!=direct[nod].end(); it++)
        if (!viz[*it]) dfsDirect(*it);
    srt.push_back(nod);
}

void dfsInvers(int nod)
{
    viz[nod]=0;
    ctc[sol].push_back(nod);
    for (it=invers[nod].begin(); it!=invers[nod].end(); it++)
        if (viz[*it]) dfsInvers(*it);
}

void citire()
{
    f >> n >> m;
    for (int i=1; i<=m; i++)
    {
        f >> x >> y;
        direct[x].push_back(y);
        invers[y].push_back(x);
    }
}

void rezolva()
{
    for (int i=1; i<=n; i++)
        if (!viz[i]) dfsDirect(i);

    for (int i=srt.size()-1; i>=0; i--)
        if (viz[srt[i]]) ++sol, dfsInvers(srt[i]);
}

void afisare()
{
    g << sol <<"\n";
    for (int i=1; i<=sol; i++)
    {
        for (int j=0; j<ctc[i].size(); j++)
            g << ctc[i][j] <<' ';
        g << "\n";
    }
}
int main()
{
    citire();
    rezolva();
    afisare();
    return 0;
}