#include <cstdio>
#include <vector>
#include <algorithm>
#define LMAX 100005
using namespace std;
FILE *fin=fopen("ctc.in","r");
FILE *fout=fopen("ctc.out","w");

bool uz[LMAX];
vector<int>G[LMAX];
vector<int>Gt[LMAX];
vector<int>ans[LMAX];
vector<int>postordine;
int n, m;
int x, y;
int nr;

void DFS1(int k)
{
    uz[k] = 1;
    for (int i=0;i<G[k].size();++i)
    {
        if (!uz[G[k][i]])
        {
            DFS1(G[k][i]);
        }
    }
    postordine.push_back(k);
}

void DFS2(int k)
{
    uz[k] = 0;
    ans[nr-1].push_back(k);
    for (int i=0;i<Gt[k].size();++i)
    {
        if (uz[Gt[k][i]])
        {
            DFS2(Gt[k][i]);
        }
    }
}

int main()
{
    fscanf(fin,"%d %d",&n,&m);
    for (int i=1;i<=m;++i)
    {
        fscanf(fin, "%d %d",&x,&y);
        G[x].push_back(y);
        Gt[y].push_back(x);
    }
    for (int i=1;i<=n;++i)
    {
        if (!uz[i])
        {
            DFS1(i);
        }
    }
    for (int i=postordine.size()-1;i>=0;i--)
    {
        if (uz[postordine[i]])
        {
            ++nr;
            DFS2(postordine[i]);
        }
    }
    fprintf(fout,"%d\n", nr);
    for (int i=0;i<nr;++i)
    {
        sort(ans[i].begin(), ans[i].end());
        for (int j=0;j<ans[i].size();++j)
        {
            fprintf(fout,"%d ",ans[i][j]);
        }
        fprintf(fout,"\n");
    }
    fclose(fin);
    fclose(fout);
    return 0;
}