#include <cstdio>
#include <vector>
#include <stack>
#include <bitset>

using namespace std;

vector<vector<int>> G, Gt, components;
bitset<100005> used;
stack<int> s;

void DFS(int k) {
  used[k] = true;

  for (auto v: G[k])
    if(!used[v])
      DFS(v);

  s.push(k);
}

void DFST(int k) {
  used[k] = true;
  components.back().emplace_back(k);
  for (auto v: Gt[k])
    if (!used[v])
      DFST(v);
}

int main()
{
  freopen("ctc.in", "r", stdin);
  freopen("ctc.out", "w", stdout);

  int N, M;
  scanf("%d%d", &N, &M);
  G.resize(N + 1);
  Gt.resize(N + 1);

  int from, to;
  for (int i = 0; i <= M; ++i) {
    scanf("%d%d", &from, &to);
    G[from].emplace_back(to);
    Gt[to].emplace_back(from);
  }

  for (int i = 1; i <= N; ++i)
    if (!used[i])
      DFS(i);
  
  used = 0;
  while (!s.empty()) {
    from = s.top();
    s.pop();
    if (used[from]) continue;
    components.emplace_back(vector<int>());
    DFST(from);
  }

  printf("%d\n", (int)components.size());
  for (auto c: components) {
    for (auto v: c)
      printf("%d ", v);
    printf("\n");
  }
  
  return 0;
}