#include<string.h> // for memset
#include<iostream> 
#include<algorithm>
#include<fstream>
#include<vector>
#define MAXNODES 100000
using namespace std;

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


vector<int> transposed_graph[MAXNODES];
vector<int> graph[MAXNODES];
vector<int> order;
bool visited[MAXNODES];
int num_nodes,num_edges;


void read(){
	int a,b;
	in>>num_nodes>>num_edges;
	for(int i=0;i<num_edges;i++){
		in>>a>>b;
		graph[a-1].push_back(b-1);
		transposed_graph[b-1].push_back(a-1);

	}
}

void dfs1(int node){
	visited[node]=true;
	for(int neighbour:graph[node]){
		if(!visited[neighbour])
			dfs1(neighbour);
	}
	order.push_back(node);
}

void dfs2(int node,vector<int>&to_add){
	visited[node]=true;
	to_add.push_back(node);
	for(int neighbour:transposed_graph[node]){
		if(!visited[neighbour]){
			dfs2(neighbour,to_add);
		}
	}
}
void solve(){

	for(int i=0;i<num_nodes;i++){
		if(!visited[i]){
			dfs1(i);
		}
	}
	memset(visited,0,sizeof(visited));
	std::reverse(order.begin(),order.end());
	vector<vector<int>> components;

	for(int a:order){
		if(!visited[a]){
			vector<int> queue;
			dfs2(a,queue);
			components.push_back(queue);
		}
	}

	out<<components.size()<<endl;

	for(const vector<int>&queue:components){
		for(int a:queue)
			out<<a+1<<" ";
		out<<endl;
	}
}

int main(){

	read();
	solve();
	return 0;
}