#include <fstream>
#include <vector>
#define NMAX 100000
using namespace std;
ifstream fin ("graf.in");
ofstream fout ("graf.out");
int n,m,nrc,nr;
vector <int> G[NMAX];
vector <int> GT[NMAX],f[NMAX];
bool viz[NMAX],postordine[NMAX];
void citire();
void DFS(int);
void DFST(int);
int main()
{int i,j;
    citire();
for (i=1;i<n;i++)
if (!viz[i]) DFS(i);
for (i=n;i>0;i--)
if (viz[postordine[i]])
{
   nrc++;
    DFST(postordine[i]);
}
fout <<nrc<<'\n';
for (i=1; i<=nrc; i++)
    {
        for (j=0; j<f[i].size();j++)
           fout<<f[i][j]<<' ';
        fout<<'\n';
     }
    return 0;
}
void citire()
{int i,x,y;
    fin>>n>>m;
    for (i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void DFS(int x)
{
    unsigned int i;
    viz[x]=1;
    for(i=1;i<=G[x].size();i++)
    if (!viz[G[x][i]])
    DFS(G[x][i]);
    postordine[++nr]=x;
}
void DFST(int x)
{
    int i;
    viz[x]=1;
    f[nrc].push_back(x);
    fout << x;
    for(i=1;i<=GT[x].size();i++)
        if(!viz[GT[x][i]])
        DFST(GT[x][i]);
}