#include <bits/stdc++.h>
#define nmax 100001
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,timp[nmax],k,nr;
vector<int>a[nmax];///-graful propriu-zis
vector<int>b[nmax];///-graful transpus
vector<int>sol[nmax];
bitset<nmax>viz;
void Citire()
{
    int i,x,y;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }
}
void DFS_Timp(int varf)
{
    int i;
    viz[varf]=1;
    for(i=0;i<a[varf].size();i++)
            if(!viz[a[varf][i]])
                DFS_Timp(a[varf][i]);
    k++;
    timp[k]=varf;
}
void DFS_Rezolvare(int varf)
{
    int i;
    viz[varf]=1;
    for(i=0;i<b[varf].size();i++)
            if(!viz[b[varf][i]])
                DFS_Rezolvare(b[varf][i]);
    sol[nr].push_back(varf);
}
void Rezolvare()
{
    int i,j;
    for(i=1;i<=n;i++)
        if(!viz[i])
            DFS_Timp(i);
    viz.reset();
    for(i=k;i>=1;i--)
        if(!viz[timp[i]])
    {
        nr++;
        DFS_Rezolvare(timp[i]);
    }
    fout<<nr<<"\n";
    for(i=1;i<=nr;i++)
    {
        sort(sol[i].begin(),sol[i].end());
        for(j=0;j<sol[i].size();j++)
                fout<<sol[i][j]<<" ";
        fout<<"\n";
    }
}
int main()
{
    Citire();
    Rezolvare();
    fin.close();
    fout.close();
    return 0;
}