#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
using namespace std;
vector <int> v[100014],t[100014],ordine;
bitset <100014> apar,viz;
fstream f,g;
int m,n,nrc;
inline void DFS (int nod)
{
    apar[nod]=1;
    int i;
    for (i=0;i<v[nod].size();i++)
        if (!apar[v[nod][i]])
            DFS(v[nod][i]);
    ordine.push_back(nod);
}
inline void df (int nod)
{
    viz[nod]=1;
    g<<nod<<" ";
    int i;
    for (i=0;i<t[nod].size();i++)
        if (!viz[t[nod][i]])
            df(t[nod][i]);
}
int main(void)
{
    f.open("ctc.in",ios::in);
    g.open("ctc.out",ios::out);
    f>>n>>m;
    int i,x,y;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        t[y].push_back(x);
    }
    // determin timpii finali
    for (i=1;i<=n;i++)
        if (!apar[i])
            DFS(i);
    // aflu componentele
    g<<"        \n";
    for (i=n-1;i>=0;i--)
        if (!viz[ordine[i]])
        {
            nrc++;
            df(ordine[i]);
            g<<"\n";
        }
    g.seekg(0,ios::beg);
    g<<nrc;
}