#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <stack>

using namespace std;

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

int n, m;
vector<int> gra[100041];
vector<int> tra[100041];

bool vi[100041];
stack<int> sta;
void defeseta(int a){
	vi[a] = true;
	for(auto b : gra[a]){
		if(!vi[b])defeseta(b);
	}
	sta.push(a);
}

vector<vector<int>> ans;
void defetista(int a, vector<int> &v){
	vi[a] = false;
	v.push_back(a);
	for(auto b : tra[a]){
		if(vi[b])defetista(b, v);
	}
}

int main(){
	// ios_base::sync_with_stdio(false);
	fin >> n >> m;
	for(int i = 0; i < m; ++i){
		int a, b;fin>> a >> b;
		gra[a].push_back(b);
		tra[b].push_back(a);
	}
	
	for(int i = 1; i <= n; ++i){
		if(!vi[i])defeseta(i);
	}
	while(!sta.empty()){
		if(vi[sta.top()]){
			ans.push_back({});
			defetista(sta.top(), ans.back());
		}
		sta.pop();
	}
	
	fout << ans.size() << "\n";
	for(auto v : ans){
		for(auto a : v){
			fout << a << " ";
		}
		fout << "\n";
	}
	return 0;
}