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

using namespace std;

const int maxn = 100005;

vector <int> g[maxn], gt[maxn];
int n, m;
bitset <maxn> used;

void dfs(int node, vector <int> &discovered) {
	used[node] = 1;
	for(auto it : g[node])
		if(!used[it])
			dfs(it, discovered);
	discovered.push_back(node);
}

void dfst(int node, vector <int> &ctc) {
	used[node] = 0;
	ctc.push_back(node);
	for(auto it : gt[node])
		if(used[it])
			dfst(it, ctc);
}

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

	fin >> n >> m;
	for(int i = 1 ; i <= m ; ++ i) {
		int x, y;
		fin >> x >> y;
		g[x].push_back(y);
		gt[y].push_back(x);
	}
	vector <int> discovered;
	for(int i = 1 ; i <= n ; ++ i)
		if(!used[i])
			dfs(i, discovered);

	reverse(discovered.begin(), discovered.end());
	
	vector <vector <int> > ctc;
	for(auto it : discovered)
		if(used[it]) {
			ctc.push_back(vector <int>());
			dfst(it, ctc.back());
		}
	fout << ctc.size() << '\n';
	for(auto comp : ctc) {
		for(auto it : comp)
			fout << it << ' ';
		fout << "\n";
	}
}