#include <fstream>
#include <vector>
#include <algorithm>

#define NMAX 100001
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

vector < int > stiva;
vector < int > G[NMAX],sol[NMAX];
vector < int > GT[NMAX];
int N,nrc[NMAX], countC=0;
bool viz[NMAX];

void dfs (int nod)
{
    viz[nod]=1;

    for(int i=0;i<G[nod].size();i++)
        if(!viz[G[nod][i]])
            dfs(G[nod][i]);

    stiva.push_back(nod);
}

void dfst( int nod )
{
    nrc[nod]=countC;
    for(int i=0;i<GT[nod].size();i++)
        if(!nrc[GT[nod][i]])
            dfst(GT[nod][i]);

}
int main()
{
    int M,i,x,y;

    f>>N>>M;
    while(M--)
    {
        f>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

    for(i=1;i<=N;i++)
        if(!viz[i])
            dfs(i);

    reverse(stiva.begin(),stiva.end());

    for(i=0;i<stiva.size();i++)
        if(!nrc[stiva[i]])
        {
            ++countC;
            dfst(stiva[i]);
        }

    for(i=1;i<=N;i++)
        sol[nrc[i]].push_back(i);

    g<<countC<<'\n';
    for(i=1;i<=countC;i++)
    {
        for(int j=0;j<sol[i].size();j++)
            g<<sol[i][j]<<' ';
        g<<'\n';
    }
}