// Include
#include <fstream>
#include <vector>
#include <stack>
using namespace std;

// Defintii
#define pb push_back

// Constante
const int sz = (int)1e5+1;

// Functii
void dfs(int node);
void printDFS(int node);

// Variabile
ifstream in("ctc.in");
ofstream out("ctc.out");

int nodes, edges;
int visited[sz];
bool inStack[sz];

vector<int> graph[sz], reversedGraph[sz];
stack<int> st;

vector< vector<int> > answer;
vector<int> answerTemp;

// Main
int main()
{
	in >> nodes >> edges;
	int rFrom, rTo;
	for(int i=1 ; i<=edges ; ++i)
	{
		in >> rFrom >> rTo;
		graph[rFrom].pb(rTo);
		reversedGraph[rTo].pb(rFrom);
	}
	
	for(int i=1 ; i<=nodes ; ++i)
		if(!inStack[i])
			dfs(i);
	
	while(!st.empty())
	{
		int current = st.top();
		st.pop();
		if(inStack[current])
		{
			printDFS(current);
			answer.pb(answerTemp);
			answerTemp.clear();
		}
	}
	
	out << answer.size() << '\n';
	
	vector< vector<int> >::iterator it, end = answer.end();
	for(it=answer.begin() ; it!=end ; ++it)
	{
		vector<int>::iterator vit, vend=it->end();
		for(vit=it->begin() ; vit!=vend ; ++vit)
			out << *vit << ' ';
		out << '\n';
	}
	
	in.close();
	out.close();
	return 0;
}

void dfs(int node)
{
	visited[node] = true;
	vector<int>::iterator it, end=graph[node].end();
	
	for(it=graph[node].begin() ; it!=end ; ++it)
		if(!visited[*it])
			dfs(*it);
	
	if(!inStack[node])
	{
		st.push(node);
		inStack[node] = true;
	}
}

void printDFS(int node)
{
	inStack[node] = false;
	answerTemp.pb(node);
	
	vector<int>::iterator it, end=reversedGraph[node].end();
	
	for(it=reversedGraph[node].begin() ; it!=end ; ++it)
		if(inStack[*it])
			printDFS(*it);
}