#include <cstdio>
#include <vector>
#define MAXN 100000

using namespace std;

vector <int> g[MAXN+1], gt[MAXN+1], con[MAXN+1];
int viz[MAXN+1], srt[MAXN+1], x, conexe;

void dfs(int nod){
  viz[nod]=1;
  for(int i=0; i<g[nod].size(); i++)
    if(viz[g[nod][i]]==0)
      dfs(g[nod][i]);
  srt[x++]=nod;
}

void dfs2(int nod){
  viz[nod]=2;
  for(int i=0; i<gt[nod].size(); i++)
    if(viz[gt[nod][i]]!=2)
      dfs2(gt[nod][i]);
  con[conexe].push_back(nod);
}

int main()
{
    FILE *fin, *fout;
    int n, m, i, y;
    fin=fopen("ctc.in", "r");
    fscanf(fin, "%d%d", &n, &m);
    for(i=0; i<m; i++){
      fscanf(fin, "%d%d", &x, &y);
      g[x].push_back(y);
      gt[y].push_back(x);
    }
    fclose(fin);
    x=0;
    for(i=1; i<=n; i++)
      if(viz[i]==0)
        dfs(i);
    for(i=n-1; i>=0; i--)
      if(viz[srt[i]]!=2){
        ++conexe;
        dfs2(srt[i]);
      }
    fout=fopen("ctc.out", "w");
    fprintf(fout, "%d\n", conexe);
    for(i=1; i<=conexe; i++){
      for(int j=0; j<con[i].size(); j++)
        fprintf(fout, "%d ", con[i][j]);
      fprintf(fout, "\n");
    }
    fclose(fout);
    return 0;
}