#include <cstdio>
#include <vector>
#define NMAX 100001
using namespace std;
FILE* fin=fopen("ctc.in","r");
FILE* fout=fopen("ctc.out","w");
vector<int> G[NMAX];
vector<int> GT[NMAX];
int n,postord[NMAX],nr,nrctc;
int ctc[NMAX];
bool viz[NMAX];
void citire();
void dfs(int x);
void dfst(int x);
void afisare();
int main()
{
    int i;
    citire();
    for (i=1; i<=n; i++)
    {
        if (!viz[i]) dfs(i);
    }
    for (i=n; i>0; i--)
    {
        if (viz[postord[i]]==1)
        {
            nrctc++;
            dfst(postord[i]);
        }
    }
    afisare();
    /*for (i=1; i<=n; i++)
        printf("%d ",postord[i]);*/
    return 0;
}
void citire()
{
    int m,i,x,y;
    fscanf(fin,"%d%d",&n,&m);
    for (i=0; i<m; i++)
    {
        fscanf(fin,"%d%d",&x,&y);
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void dfs(int x)
{ int i;
    viz[x]=1;
    //parcurg lista de adiacenta a lui x;
    for (i=0; i<G[x].size(); i++)
        if (!viz[G[x][i]]) dfs(G[x][i]);
    postord[++nr]=x;
}
void dfst(int x)
{
    int i;
    viz[x]=0;
    ctc[x]=nrctc;
    for (i=0; i<GT[x].size(); i++)
        if (viz[GT[x][i]]==1) dfst(GT[x][i]);
}
void afisare()
{
    int i,j;
    fprintf(fout,"%d\n",nrctc);
    for (i=1; i<=nrctc; i++)
    {
        for (j=1; j<=n; j++)
        {
            if (ctc[j]==i) fprintf(fout,"%d ",j);
        }
        fprintf(fout,"\n");
    }
}