#include <cstdio>
#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>
#include <cstring>

using namespace std;

#define maxN 100005
#define PB push_back

int N , M , cost[maxN] , comp , step;
bool in_S[maxN];


vector <int> lista[maxN] , sol[maxN];
stack <int> P , S;


void get_component (int node)
{
	++comp;
	
	while (!S.empty () && S.top () != node)
	{
		sol[comp].PB (S.top ());
		
		in_S[S.top ()] = false;
		S.pop ();
	}
	
	if (!S.empty ())
	{
		sol[comp].PB (S.top ());
		
		in_S[S.top ()] = false;
		S.pop ();
	}
}


void pop_useless (int reference)
{
	while (!P.empty () && cost[P.top ()] > reference)
		P.pop ();
}


void Gabow (int X)
{
	cost[X] = step;
	
	++step;
	
	S.push (X);
	P.push (X);
	
	in_S[X] = true;
	
	for (unsigned int i = 0 ; i < lista[X].size () ; ++i)
	{
		int nodcur = lista[X][i];
		
		if (cost[nodcur] == -1)
			Gabow (nodcur);
		
		else
		{	
			if (in_S[nodcur])
				pop_useless (cost[nodcur]);
		}
	}
	
	if (!P.empty () && X == P.top ())
	{
		get_component (X);
		P.pop ();
	}
}


int main ()
{
	freopen ("ctc.in" , "r" , stdin);
	freopen ("ctc.out" , "w" , stdout);
	
	scanf ("%d %d" , &N , &M);
	
	
	int a , b;
	
	for (int i = 1 ; i <= M ; ++i)
	{
		scanf ("%d %d" , &a , &b);
		
		lista[a].PB (b);
	}
	
	memset (cost , -1 , sizeof (cost));
	
	for (int i = 1 ; i <= N ; ++i)
		if (cost[i] == -1)
			Gabow (i);
	
	/*for (int i = 1 ; i <= N ; ++i)
		cout << cost[i] << " ";*/

	
	printf ("%d\n" , comp);
	
	for (int t = 1 ; t <= comp ; ++t)
	{
		for (unsigned int i = 0 ; i < sol[t].size () ; ++i)
			printf ("%d " , sol[t][i]);
		
		printf ("\n");
	}
	
	return 0;
}