#include <fstream>
#include <vector>
 
using namespace std;
 
ifstream in("ctc.in");
ofstream out("ctc.out");
 
const int Max = 100010;
 
vector<int> g[Max],gt[Max];
vector<vector<int> > comp;
int q[Max],nr;
char vaz[Max];
 
void dfs1(int nod)
{
	    vaz[nod] = 1;
		    for(vector<int>::iterator it = g[nod].begin(); it != g[nod].end(); it++)
				        if(!vaz[*it])
							            dfs1(*it);
			 
			    q[++nr] = nod;

}
 
void dfs2(int nod,vector<int> &comp)
{
	    vaz[nod] = 0;
		    comp.push_back(nod);
			    for(vector<int>::iterator it = gt[nod].begin(); it != gt[nod].end(); it++)
					        if(vaz[*it])
								            dfs2(*it,comp);

}
 
int main()
{
	    int n,m,x,y;
		    in >> n >> m;
			    for(int i = 1; i <= m; i++)
				{
					        in >> x >> y;
							        g[x].push_back(y);
									        gt[y].push_back(x);
											    
				}
				 
				    for(int i = 1; i <= n; i++)
						        if(!vaz[i])
									            dfs1(i);
					    for(int i = nr; i; i--)
							        if(vaz[q[i]])
									{
										            comp.push_back(vector<int>());
													            dfs2(q[i],comp.back());
																        
									}
						    out << comp.size() << "\n";
							 
							    for(int i = 0; i < comp.size(); i++)
								{
									        for(int j = 0; j < comp[i].size(); j++)
												            out << comp[i][j] << " ";
											        out << "\n";
													    
								}
								    return 0;

}