#include <fstream>
#include <vector>
#include<algorithm>

using namespace std;

vector <int> G[100100], GT[100100], S[100100], A;//G-graful initial GT -graful transpus
int N, M, T[100100], Sol, Nr;
int viz[100100];

//parcugerea in adancime
void df (int x) 
{
	viz[x] = 1;
 	for (int i = 0; i < (int) G[x].size(); ++ i)
		if (!viz[G[x][i]])
			df(G[x][i]);
    
	T[x] = ++ Nr;  //T[x] ne spune din ce componenta conexa face parte x
}

//parcurgerea grafului transpus
void df2 (int x) 
{
	S[Sol].push_back(x);//x este adaugat la componenta tare conexa Sol
	viz[x] = 1;
	for (int i = 0; i < (int) GT[x].size(); ++ i)
		if (!viz[GT[x][i]])
			df2(GT[x][i]);
}

inline bool cmp (int a, int b) {
	return T[a] > T[b];
}

int main () {
    int i, a, b, j;
    
	ifstream f("ctc.in");
	ofstream g("ctc.out");
    
    
	f>>N>>M;
	for (i = 1; i <= M; ++ i) {
		f>>a>>b;
		G[a].push_back(b);
		GT[b].push_back(a);
	}
    
	/*for (i = 1; i <= N; ++ i)
		if (!viz[i])
            df (i);
    */
	for (i = 1; i <= N; ++ i)
		A.push_back(i);//adauga pe i la vectorul A
    
	sort(A.begin(), A.end(), cmp);
    
//	viz.reset ();
    for(i=1;i<=N;i++)
        viz[i]=0;
    
    // parcurgerea in adancime pt graful transpus
	for (i = 0; i < N; ++ i)
		if (!viz[A[i]]) {
			Sol ++;
			df2 (A[i]);       
		}
	g<<Sol<<"\n";
    
    // afisare solutie   
	for (i = 1; i <= Sol; ++ i) {
        // afisam componenta  a i-a
    	for (j = 0; j < (int) S[i].size(); ++ j)
			g<<S[i][j]<<" ";
        g<<"\n";
        
	}
	f.close();
	g.close();
}