#include <fstream>
#include <vector>

using namespace std;

#define NM 100005

int n,m,t[NM], p, viz[NM], k;
vector<int> G[NM], GT[NM], ctc[NM];
ifstream fin("ctc.in");
ofstream fout("ctc.out");
void DFS(int x)
{
    int i, w;

    viz[x] = 1;
    for (i = 0;i< G[x].size();i++)
        {
            w=G[x][i];
            if (!viz[w])
                DFS(w);
        }
    p++;t[p] = x;
}

void DFST(int x)
{
    int i, w;

    viz[x] = k; ctc[k].push_back(x);
    for (i = 0;i<GT[x].size(); i++)
    {
        w=GT[x][i];
        if (!viz[w])
            DFST(w);
    }

}

int main()
{
    int i,j, x, y;
    fin>>n>>m;
    for (i=1;i<=m;i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

    for (i = 1; i <= n; i++)
        if (!viz[i])
            DFS(i);
    for(i=1;i<=n;i++)
        viz[i]=0;
    for (i = n; i>=1; i--)
        if (!viz[t[i]])
        {
            k++;
            DFST(t[i]);
        }

    fout<<k<<endl;
    for (i = 1; i <= k; i++)
    {
        for (j=0; j < ctc[i].size(); j++)
            fout<<ctc[i][j]<<' ';
        fout<<endl;
    }

    return 0;
}