#include <fstream>
#include <vector>
#include <string.h>

#define max_n 100001

using namespace std;

int i,n,m,x,y,nst,rez;
vector <int> g[max_n];
vector <int> gt[max_n];
vector <int>::iterator it;
bool u[max_n];
int st[max_n];
vector <int> sol[max_n];

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

void DF1(int x) {
	vector <int>::iterator it;
	u[x]=true;
	for (it=g[x].begin(); it!=g[x].end(); it++) 
		if (!u[*it]) DF1(*it);
	st[nst++]=x;
}

void DF2(int x) {
	vector <int>::iterator it;
	u[x]=true;
	sol[rez].push_back(x);
	for (it=gt[x].begin(); it!=gt[x].end(); it++) 
		if (!u[*it]) DF2(*it);
}

int main () {
	in >> n >> m;
	for (i=1; i<=m; i++) {
		in >> x >> y;
		g[x].push_back(y);
		gt[y].push_back(x);
	}
	
	nst=rez=0;
	memset(u,false,sizeof(u));
	for (i=1; i<=n; i++) 
		if (!u[i]) 
			DF1(i);
		
	memset(u,false,sizeof(u));
	for (i=n-1; i>=0; i--) 
		if (!u[st[i]]) {
			DF2(st[i]);
			rez++;
 		}
	
	out << rez << '\n';
	for (i=0; i<rez; i++) {
		for (it=sol[i].begin(); it!=sol[i].end(); it++)
			out << *it << ' ';
		out << '\n';
	}
	return 0;
}