#include<cstdio>
#include <vector>
#define NMAX 100010
#define IN "ctc.in"
#define OUT "ctc.out"
using namespace std;

int n,m,nr,ctc;
int viz[NMAX],pord[NMAX];

vector <int> G[NMAX];
vector <int> Gt[NMAX];
vector <int>M[NMAX];

void citire();
void dfs(int);
void dfst(int);
void afisare();


int main()
{
    int i;
    citire();
    nr=0;
    for(i=1; i<=n; i++)
        if(!viz[i]) dfs(i);

    for(i=n; i>=1; i--)
        if(viz[pord[i]])
        {
            dfst(pord[i]);
            ctc++;
        }

    afisare();
    return 0;
}


void citire()
{
    int i,x,y;
    FILE*fin=fopen(IN,"r");
    fscanf(fin,"%d%d",&n,&m);
    for(i=1; i<=m; i++)
    {
        fscanf(fin,"%d%d",&x,&y);
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    fclose(fin);
}

void dfs(int vf)
{
    int i,nra;
    nra=G[vf].size();
    viz[vf]=1;
    for(i=0; i<nra; i++)
        if(!viz[G[vf][i]])
            dfs(G[vf][i]);
    pord[++nr]=vf;
}

void dfst(int vf)
{
    int i,nra;
    nra=Gt[vf].size();
    viz[vf]=0;
    M[ctc].push_back(vf);
    for(i=0; i<nra; i++)
        if(viz[Gt[vf][i]])
            dfst(Gt[vf][i]);

}
void afisare()
{
    int i,j,lg;
    FILE*fout=fopen(OUT,"w");
    fprintf(fout,"%d",ctc);
    fprintf(fout,"%s","\n");
    for(i=0; i<ctc; i++)
    {
        lg=M[i].size();
        for(j=0; j<lg; j++)
            fprintf(fout,"%d ",M[i][j]);

        fprintf(fout,"%s","\n");
    }
    fclose(fout);
}