#include<stdio.h>
#include<string>
#include<vector>
using namespace std;
FILE*fin=fopen("ctc.in","r");
FILE*fout=fopen("ctc.out","w");
#define nm 100005
#define pb push_back 
int n,m,stiva[nm],nrctc=0,ds=0;
char viz[nm];
vector<int> g[nm],gt[nm],ctc[nm];
void df(int nod)
{
    viz[nod]=1;
    int i,nnod;
    for(i=0;i<g[nod].size();i++)
    {
        nnod=g[nod][i];
        if(!viz[nnod]) df(nnod);
    }
    ds++;stiva[ds]=nod;
}
void dft(int nod)
{
    viz[nod]=0;
    ctc[nrctc].pb(nod);
    int i,nnod;
    for(i=0;i<gt[nod].size();i++)
    {
        nnod=gt[nod][i];
        if(viz[nnod]) dft(nnod);
    }
}
int main()
{
    int a,b,i,j;
    fscanf(fin,"%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        fscanf(fin,"%d%d",&a,&b);
        g[a].pb(b);
        gt[b].pb(a);
    }
    memset(viz,0,sizeof(viz));
    for(i=1;i<=n;i++)
        if(!viz[i]) df(i);
    for(i=n;i>=1;i--)
        if(viz[stiva[i]])
        {
            nrctc++;
            dft(stiva[i]);
        }
    fprintf(fout,"%d\n",nrctc);
    for(i=1;i<=nrctc;i++)
    {
        for(j=0;j<ctc[i].size();j++)
            fprintf(fout,"%d ",ctc[i][j]);
        fprintf(fout,"\n");
    }
    fclose(fin);
    fclose(fout);
    return 0;
}