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

FILE *f=fopen ("ctc.in","r");
FILE *g=fopen ("ctc.out", "w");

vector <int> G[100001],Gt[100001],C[100001];
int ord[100001],viz[100001],nr;
int nrc;

void dfs(int x)
{
    viz[x]=1;
    vector <int>::iterator it;
    for(it=G[x].begin(); it!=G[x].end(); it++)
    {
        if(!viz[*it])
        dfs(*it);
    }
    ord[++nr]=x;
}
void dfst (int x)
{
    viz[x]=0;
    C[nrc].push_back(x);
    vector <int>::iterator it;
    for(it=Gt[x].begin(); it!=Gt[x].end(); it++)
        if(viz[*it])
            dfst(*it);

}


int main()
{
    int n,m,x,y,i;

    fscanf(f,"%d%d",&n,&m);

    while(m--)
    {
        fscanf (f,"%d%d",&x,&y);
        G[x].push_back(y);
        Gt[y].push_back(x);
    }

    for(i=1; i<=n; i++)
    {
        if(!viz[i])
        dfs(i);
    }
    for(i=n; i>=1; i--)
    {
        if(viz[ord[i]])
        {
            nrc++;
            dfst(ord[i]);
        }

    }
    fprintf(g,"%d\n",nrc );

    vector <int>::iterator it;
    for(i=1; i<=nrc; i++)
    {
        for(it=C[i].begin(); it!=C[i].end(); it++)
        {
            fprintf(g,"%d ",*it);
        }
        fprintf(g,"\n");
    }



    return 0;
}