#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

short viz[100005];
vector <int> v[100005];
vector <int> inv[100005];
vector <int> sol[100005];
vector <int> f;
int n,m;
int nr;

void dfs(int nod)
{
    viz[nod]=1;
    for(auto& i : v[nod])
        if(viz[i]!=1)
            dfs(i);
    f.push_back(nod);
}
void inv_dfs(int nod)
{
    viz[nod]=-1;
    sol[nr].push_back(nod);
    for(auto& i : inv[nod])
        if(viz[i]!=-1)
            inv_dfs(i);
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int x,y;
        fin>>x>>y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(viz[i]!=1)
            dfs(i);

    for(int i=n-1;i>=0;i--)
        if(viz[f[i]]!=-1)
            nr++,inv_dfs(f[i]);

    fout<<nr<<'\n';
    for(int i=1;i<=nr;i++)
    {
        for(auto& j : sol[i])
            fout<<j<<' ';
        fout<<'\n';
    }


}