#include <iostream>
#include <fstream>
#include <vector>
#include<stack>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

vector <int> L1[100001];
vector <int> L2[100001];
vector < vector <int> > sol;
vector <int> vec;
stack <int> stiva;
vector <int> comp;

bool viz1[100001], viz2[100001];
int n, m, x, y, nr;

/// pas 1 citire si bagare in L1 si L2

void citire()
{
    f>>n>>m;

    for(int i=1; i<=m; i++)
    {
        f>>x>>y;
        L1[x].push_back(y);
        L2[y].push_back(x);
    }
}

/// pas 2 scriere DFS1 si DFS2 una pe L1 si una pe L2

void DFS1(int k)
{
    viz1[k]=1;
    for(int i=0; i<L1[k].size(); i++)
    {
        int nod=L1[k][i];
        if(viz1[nod]==0)
            DFS1(nod);
    }
    vec.push_back(k);
}

void DFS2(int k)
{
    viz2[k]=1;
    for(int i=0; i<L2[k].size(); i++)
    {
        int nod=L2[k][i];
        if(viz2[nod]==0)
            DFS2(nod);
    }
    comp.push_back(k);
}

/// pas 3 functia rezolva care va fi alcatuita din 2 bucatele
/// prima bucatica e sa parcurgi ca pe componentele conexe normale cu DFS1
/// a doua parte explic eu

void rezolva()
{
    for(int j=1; j<=n; j++)
        if(viz1[j]==0)
            DFS1(j);

    while(!stiva.empty())
    {
        int t = stiva.top();
        stiva.pop();
        comp.clear();
        if(viz2[t]==0)
        {
            // cout << vec[t] << " ";
            DFS2(t);
            sol.push_back(comp);
        }

    }

}

/// pas 4
/// scrie main ()
/// afisarea ?? la ce -> da-ti seama din enuntul problemei ce trebuie afisat
/// si declarati o matrice sau vectori sau ceva care sa salveze chestiile

void afisare()
{
    g<<sol.size()<<endl;
    for(int l=0; l<sol.size(); l++)
    {
        for(int l2=0; l2<sol[l].size(); l2++)
            g<<sol[l][l2]<<" ";
        g<<endl;
    }
}

/// pas 5
/// intelegem

int main()
{
    citire();
    rezolva();
    afisare();
    return 0;
}