#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,ctc[NMAX+1];

vector<int> g[NMAX+1], gt[NMAX+1];
bool viz1[NMAX+1],viz2[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 dfs1(int nod)
{
    viz1[nod]=1;
    for(int x:g[nod])
        if(viz1[x]==0)
            dfs1(x);
}

void dfs2(int nod)
{
    viz2[nod]=1;
    for(int x:gt[nod])
        if(viz2[x]==0)
            dfs2(x);
}

void comp_tare_conexe()
{
    for(int i=1; i<=n; i++)
        if(ctc[i]==0)
        {
            nrc++;
            dfs1(i);
            dfs2(i);
            for(int j=1; j<=n; j++)
            {
                if(viz1[j]&&viz2[j])
                    ctc[j]=nrc;
                viz1[j]=viz2[j]=0;
            }
        }
}

int main()
{
    citire();
    comp_tare_conexe();
    fout<<nrc<<'\n';
    for(int i=1;i<=nrc;i++)
    {
        for(int j=1;j<=n;j++)
            if(ctc[j]==i)
            fout<<j<<' ';
        fout<<'\n';
    }

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