#include <fstream>
#include <vector>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m,i,used[100001],used2[100001],x,y,j,cont;
vector <int> nod[100001],nod2[100001],Exit,ctc,comp[100001];

int dfs(int x)
{
    used[x]=1;
    for(int i=0;i<nod[x].size();i++)
        if(!used[nod[x][i]])
        {
            dfs(nod[x][i]);
        }
    Exit.push_back(x);
    return 0;
}
int dfs2(int x,vector <int>& V)
{
    used2[x]=1;
    V.push_back(x);
    for(int i=0;i<nod2[x].size();i++)
        if(!used2[nod2[x][i]])
        {
            dfs2(nod2[x][i],V);
        }
    return 0;
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        nod[x].push_back(y);
        nod2[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        if(!used[i])
            dfs(i);
    for(j=n-1;j>=0;j--)
    {
        if(!used2[Exit[j]])
        {
            dfs2(Exit[j],ctc);
            comp[cont++]=ctc;
            ctc.erase(ctc.begin(),ctc.end());
        }
    }
    fout<<cont<<'\n';
    for(i=0;i<cont;i++)
        {
        for(j=0;j<comp[i].size();j++)
            fout<<comp[i][j]<<" ";
        fout<<'\n';
        }
    return 0;
}