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

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

const int NMAX = 100000;

int m, n, nrc;

vector<int> g[NMAX+1], gt[NMAX+1], ctc[NMAX+1],post;
bool viz[NMAX+1];

void citire()
{
    int x,y;
    fin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
}

void dfs(int nod)
{
    viz[nod]=1;
    for(int x:g[nod])
        if(viz[x]==0)
            dfs(x);
    post.push_back(nod);
}

void dfsgt(int nod)
{
    viz[nod]=0;
    ctc[nrc].push_back(nod);
    for(int x:gt[nod])
        if(viz[x]==1)
            dfsgt(x);
}

void comp_tare_conexe()
{
    int i;
    for(i=1; i<=n; i++)
        if(viz[i]==0)
            dfs(i);
    for(i=post.size()-1; i>=0; i--)
        if(viz[post[i]]==1)
        {
            nrc++;
            dfsgt(post[i]);
        }
}

void afisare()
{
    fout<<nrc<<'\n';
    for(int i=1; i<=nrc; i++)
    {
        for(int x:ctc[i])
            fout<<x<<' ';
        fout<<'\n';
    }
}

int main()
{
    citire();
    comp_tare_conexe();
    afisare();

    fin.close();
    fout.close();
    return 0;
}