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

using namespace std;

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

const int MAXN = 100000;

vector<int> g[MAXN + 1], tg[MAXN + 1], order, noduri[MAXN + 1];
int viz[MAXN + 1], ctc;

void dfs(int node) {
  viz[node] = 1;
  for(int vecin : g[node]) {
    if(!viz[vecin]) {
      dfs(vecin);
    }
  }
  order.push_back(node);
}

void dfs2(int node) {
  viz[node] = 1;
  noduri[ctc].push_back(node);
  for(int vecin : tg[node]) {
    if(!viz[vecin]) {
      dfs2(vecin);
    }
  }
}

int main() {
  int n, m;
  fin >> n >> m;
  for(int i = 1; i <= m; i++) {
    int u, v;
    fin >> u >> v;
    g[u].push_back(v);
    tg[v].push_back(u);
  }

  for(int i = 1; i <= n; i++) {
    if(!viz[i]) {
      dfs(i);
    }
  }

  for(int i = 1; i <= n; i++) {
    viz[i] = 0;
  }

  for(int i = n - 1; i >= 0; i--) {
    if(!viz[order[i]]) {
      ctc++;
      dfs2(order[i]);
    }
  }

  fout << ctc << "\n";
  for(int i = 1; i <= ctc; i++) {
    for(int nod : noduri[i]) {
      fout << nod << " ";
    }
    fout << "\n";
  }

  return 0;
}