//#include <iostream>
#include <fstream>
#include <vector>

// KOSARAJU 2xDFS++

using namespace std;

ifstream f("ctc.in");
ofstream cout("ctc.out");

int n, m, viz[100005], pre[100005], nr=0, k;
vector <int> v[100005];
vector <int> vt[100005];
vector <int> sol[100005];

void dfs(int i)
{
  int j;
  viz[i]=1;
  for (j=0; j<vt[i].size(); j++)
    if (viz[vt[i][j]]==0) dfs(vt[i][j]);
  //k++;
  pre[++k]=i;
}

void dfsr(int i)
{
    int j;
    sol[nr].push_back(i);
    viz[i]=0;
    for (j=0; j<v[i].size(); j++)
      if (viz[v[i][j]]==1) dfsr(v[i][j]);
}
int main()
{
    int i, j, x, y;

    f>>n>>m;

    for (i=1; i<=m; i++)
    {
        f>>x>>y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }

    for (i=1; i<=n; i++)
      if (viz[i]==0)
      {
          //nr++;
          dfs(i);
      }

    for (i=n; i>=1; i--)
      if (viz[pre[i]]==1)
      {
          nr++;
          dfsr(pre[i]);
      }
    cout<<nr<<"\n";

    for (i=1; i<=k; i++)
    {
        for (j=0; j<sol[i].size(); j++) cout<<sol[i][j]<<" ";
        cout<<"\n";
    }
    return 0;
}