#include <fstream>
#include <vector>

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

const int max_n=100005;

int n,m;

vector <int> grafn[max_n],graftrans[max_n],con[max_n];

int st[max_n],k=0,nrcon;

bool viz[max_n];

void dfnormal(int nod)
{
    viz[nod]=1;
    for(int i=0;i<grafn[nod].size();i++)
     if(!viz[grafn[nod][i]]) dfnormal(grafn[nod][i]);
    st[k]=nod;
    k++;
}

void dftrans(int nod)
{
    viz[nod]=0;
    con[nrcon].push_back(nod);
    for(int i=0;i<graftrans[nod].size();i++)
     if(viz[graftrans[nod][i]]) dftrans(graftrans[nod][i]);

}
int main()
{
    freopen ("ctc.in","r",stdin);
    freopen ("ctc.out","w",stdout);
    scanf("%d%d",&n,&m);
    //f>>n>>m;
    for(int i=1;i<=m;i++)
     {
         int a,b;
         scanf("%d%d",&a,&b);
        // f>>a>>b;
         grafn[a].push_back(b);
         graftrans[b].push_back(a);
     }
     for(int i=1;i<=n;i++)
       if(!viz[i]) dfnormal(i);

    nrcon=1;
    for(int i=n-1;i>=0;i--)
     if(viz[st[i]])
     {
         dftrans(st[i]);
         nrcon++;
     }

     printf("%d",nrcon);
    // g<<nrcon;
    for(int i=0;i<nrcon;i++)
     {
         for(int j=0;j<con[i].size();j++)
           printf("%d ",con[i][j]);
           //   g<<con[i][j]<<" ";
          printf("\n");
          //g<<"\n";
     }

    return 0;
}