#include <cstdio>
#include <cmath>
#include <climits>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <bitset>
#include <map>
#include <cstring>
#include <algorithm>

#define NMAX 100003

using namespace std;

FILE* fin, * fout;

int n, m, niv,nrc;
int topo[NMAX];
bool viz[NMAX];
vector<int>graf[NMAX];
vector<int>grafTrans[NMAX];
vector<int>compConex[NMAX];

void dfs1(int nod)
{
	viz[nod] = true;
	for (int i = 0; i < graf[nod].size(); i++)
	{
		int nd = graf[nod][i];
		if (!viz[nd])
		{
			dfs1(nd);
		}
	}
	topo[++niv] = nod;
}
void dfs2(int nod)
{
	viz[nod] = true;
	compConex[nrc].push_back(nod);
	for (int i = 0; i < grafTrans[nod].size(); i++)
	{
		int nd = grafTrans[nod][i];
		if (!viz[nd])
		{
			dfs2(nd);
		}
	}
}

int main()
{
	fin = fopen("ctc.in", "r");
	fout = fopen("ctc.out", "w");
	
	fscanf(fin, "%d %d", &n, &m);
	for (int i = 1; i <= m; i++)
	{
		int x, y;
		fscanf(fin, "%d %d", &x, &y);
		graf[x].push_back(y);
		grafTrans[y].push_back(x);
	}
	for (int i = 1; i <= n; i++)
	{
		if (!viz[i])
		{
			dfs1(i);
		}
	}
	for (int i = 1; i <= n; i++)
	{
		viz[i] = false;
	}

	//parcurg invers topologic
	for (int i = n; i >=1; i--)
	{
		int nd = topo[i];
		if (!viz[nd])
		{
			nrc++;
			dfs2(nd);
		}
	}
	fprintf(fout, "%d\n", nrc);
	for (int i = 1; i <= nrc; i++)
	{
		for (int j = 0; j < compConex[i].size(); j++)
		{
			fprintf(fout, "%d ", compConex[i][j]);
		}
		fprintf(fout, "\n");
	}
	return 0;
}