#include <bits/stdc++.h>
#define NMAX 100001

using namespace std;

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

int n, m,nrc;
vector<int> edge[NMAX],revedge[NMAX];
vector<int>popn;
vector<int> ans[NMAX];
bitset<NMAX> viz;

void DFS(int x)
{
	viz[x] = 1;
	for (int i : edge[x])
		if (!viz[i])
			DFS(i);
	popn.push_back(x);
}
void DFSREV(int x)
{
	viz[x] = 1;
	ans[nrc - 1].push_back(x);
	for (int i : revedge[x])
		if (!viz[i])
			DFSREV(i);
}
int main()
{
	int x, y;
	fin >> n >> m;
	while (m--)
	{
		fin >> x >> y;
		edge[x].push_back(y);
		revedge[y].push_back(x);
	}
	for(int i = 1; i <= n; i++)
		if (!viz[i])
			DFS(i);
	viz.reset();
	for(vector<int>::reverse_iterator it = popn.rbegin(); it != popn.rend(); it++)
		if (!viz[*it])
		{
			nrc++;
			DFSREV(*it);
		}
	
	fout << nrc << "\n"; 
	for (int i = 0; i <= ans->size(); i++)
		sort(ans[i].begin(), ans[i].end());
	for (int i = 0; i < nrc; i++) {
		for (int j : ans[i])
			fout << j << " ";
		fout << "\n";
	}

	fin.close();
	fout.close();
	return 0;
}