#include<bits/stdc++.h>
using namespace std;

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


int num_nodes,num_edges;
vector<int> graph[100000];
vector<int> transposed[100000];
vector<int> order;
bool visited[100000];

void read(){
	in>>num_nodes>>num_edges;
	int a,b;

	for(int i=0;i<num_edges;i++){
		in>>a>>b;
		graph[a-1].push_back(b-1);
		transposed[b-1].push_back(a-1);
	}
}


void dfs1(int node){
	visited[node]=true;
	for(int i=0;i<graph[node].size();i++)
		if(!visited[graph[node][i]])
			dfs1(graph[node][i]);

	order.push_back(node);
}

void dfs2(int node,vector<int>&to_add){
	visited[node]=true;
	to_add.push_back(node);
	for(int i=0;i<transposed[node].size();i++)
		if(!visited[transposed[node][i]])
			dfs2(transposed[node][i],to_add);
}


void kosaraju(){
	for(int i=0;i<num_nodes;i++)
		if(!visited[i])
			dfs1(i);

	for(int i=0;i<num_nodes;i++)
		visited[i]=false;

	vector<vector<int>> result;
	for(int i=order.size()-1;i>=0;i--){
		int node=order[i];
		if(!visited[node]){
			vector<int> results;
			dfs2(node,results);
			result.push_back(results);
		}
	}
	out<<result.size()<<'\n';
	for(const vector<int>&a:result){
		for(int p:a)
			out<<p+1<<" ";
		out<<'\n';
	}

}


int main(){
	read();
	kosaraju();;
	return 0;
}