#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100002
using namespace std;
ifstream  fin("ctc.in");
ofstream fout("ctc.out");
int n,m,nrctc,viz[NMAX];
stack<int> stiva;
vector<int> graph[NMAX],graph_tr[NMAX],comp[NMAX];

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

    int a,b;
    for(int i=1; i<=m; i++)
    {
        fin>>a>>b;
        graph[a].push_back(b);
        graph_tr[b].push_back(a);
    }
}

void DFS1(int nod)
{
    viz[nod]=1;
    for(int i=0; i<graph[nod].size(); i++)
    {
        int next_nod=graph[nod][i];
        if(!viz[next_nod])
        {
            DFS1(next_nod);
        }
    }
    stiva.push(nod);
}

void DFS2(int nod)
{
    viz[nod]=0;
    comp[nrctc].push_back(nod);
    for(int i=0; i<graph_tr[nod].size(); i++)
    {
        int next_nod=graph_tr[nod][i];
        if(viz[next_nod])
        {
            DFS2(next_nod);
        }
    }
}

int main()
{
    citire();

    for(int i=1; i<=n; i++)
    {
        if(!viz[i])
        {
            DFS1(i);
        }
    }

    nrctc=0;
    while(!stiva.empty())
    {
        int nod=stiva.top();
        stiva.pop();

        if(viz[nod])
        {
            nrctc++;
            DFS2(nod);
        }
    }

    fout<< nrctc << "\n";

    for(int i=1; i<=nrctc; i++)
    {
        for(int j=0; j<comp[i].size(); j++)
        {
            fout<< comp[i][j] << " ";
        }
        fout<< "\n";
    }

    return 0;
}