#include <fstream>
#include <vector>

using namespace std;

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

const int N = 100000 + 5;

int n, m, va[N], vb[N];
vector<int>A[N];
vector<int>B[N];
int st[N], vf = 0;

inline void da(int a)
{
  va[a] = 1;
  for (auto b : A[a])
  {
    if (va[b] == 0)
    {
      da(b);
    }
  }
  st[++vf] = a;
}

int k;

vector<int>lol[N];

inline void db(int a)
{
  lol[k].push_back(a);
  vb[a] = 1;
  for (auto b : B[a])
  {
    if (vb[b] == 0)
    {
      db(b);
    }
  }
}

int main()
{
  fin >> n >> m;
  for (int i = 1; i <= m; i++)
  {
    int a, b;
    fin >> a >> b;
    A[a].push_back(b);
    B[b].push_back(a);
  }
  for (int i = 1; i <= n; i++)
  {
    if (va[i] == 0)
    {
      da(i);
    }
  }
  for (int i = n; i >= 1; i--)
  {
    int x = st[i];
    if (vb[x] == 0)
    {
      k++;
      db(x);
    }
  }
  fout << k << "\n";
  for (int i = 1; i <= k; i++)
  {
    for (auto x : lol[i])
    {
      fout << x << " ";
    }
    fout << "\n";
  }
  return 0;
}