#include <cstdio>
#include <vector>
#include <deque>

using namespace std;
FILE *f,*g;

vector <int> v[100002],vt[100002],sol[100002];
bool viz[100002];
int q[100002];


void euler(int nod)
{
    viz[nod]=1;
    for(int i=0;i<v[nod].size();++i)
        if(!viz[v[nod][i]])
            euler(v[nod][i]);
   q[++q[0]]=nod;
}
void euler1(int nod,int no)
{
    viz[nod]=1;
    for(int i=0;i<vt[nod].size();++i)
            if(!viz[vt[nod][i]])
                euler1(vt[nod][i],no);
    sol[no].push_back(nod);
}
int main()
{
    f=fopen("ctc.in","r");
    g=fopen("ctc.out","w");
    int m,n,x,y;
    fscanf(f,"%d %d",&n,&m);
    for(int i=1;i<=m;++i)
    {
        fscanf(f,"%d %d",&x,&y);
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for(int i=1;i<=n;++i)
        if(!viz[i])
            euler(i);
    for(int i=1;i<=n;++i)
        viz[i]=0;
    int nr=0;
    for(int i=q[0];i>0;--i)
        if(!viz[q[i]])
            euler1(q[i],++nr);
    fprintf(g,"%d\n",nr);
    for(int i=1;i<=nr;++i)
    {
        for(int j=0;j<sol[i].size();++j)
            fprintf(g,"%d ",sol[i][j]);
        fprintf(g,"\n");
    }
    fclose(f);
    fclose(g);
    return 0;
}