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

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

vector<int> graph[100000];
vector<int> transposed_graph[100000];
bool visited[100000];
vector<int> order;
int node_count;


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


int dfs1(int node){
	visited[node]=true;
	for(int i=0;i<graph[node].size();i++){
		int there=graph[node][i];
		if (!visited[there])
			dfs1(there);
	}
	order.push_back(node);
}
int dfs2(int node,vector<int>&to_fill){
	visited[node]=true;
	to_fill.push_back(node);
	for(int i=0;i<transposed_graph[node].size();i++){
		int there=transposed_graph[node][i];
		if(!visited[there])
			dfs2(there,to_fill);
	}
}

void solve(){
	int cnt=0;
	for(int i=0;i<node_count;i++){
		if(!visited[i])
			dfs1(i);
	}
	for(int i=0;i<node_count;i++)
		visited[i]=false;
	
	vector<vector<int>> connected;

	for(int k=node_count-1;k>=0;k--){
		if(!visited[order[k]]){
			vector<int> result;
			dfs2(order[k],result);
			connected.push_back(result);
		}
	}

	out<<connected.size()<<endl;
	for(int i=0;i<connected.size();i++){
		for(int a:connected[i])
			out<<a+1<<" ";
		out<<'\n';
	}
}

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