#include <cstdio>
#include <cstring>
#include <vector>
using namespace std;
int n,m,cnt;
vector <int> succ[100100],pred[100100],comp[100100];
bool marc[100100],v[100100];

void dfs(int nod)
{
	v[nod]=1;
	for (int i=0;i<succ[nod].size();++i)
		if (!v[succ[nod][i]])
			dfs(succ[nod][i]);
}

void dfsinv(int nod)
{
	marc[nod]=1;
	for (int i=0;i<pred[nod].size();++i)
		if (!marc[pred[nod][i]]&&v[pred[nod][i]])
		{
			comp[cnt].push_back(pred[nod][i]);
			dfsinv(pred[nod][i]);
		}
}

void conex()
{
	for (int i=1;i<=n;++i)
		if (!marc[i])
		{
			comp[++cnt].push_back(i);
			memset(v,0,sizeof(v));
			dfs(i);
			dfsinv(i);
		}
}

void citire()
{
	scanf("%d%d",&n,&m);
	int x,y;
	for (int i=1;i<=m;++i)
	{
		scanf("%d%d",&x,&y);
		succ[x].push_back(y);
		pred[y].push_back(x);
	}
}

void scrie()
{
	printf("%d\n",cnt);
	for (int i=1;comp[i].size();++i)
	{
		for (int j=0;j<comp[i].size();++j)
			printf("%d ",comp[i][j]);
		printf("\n");
	}
}

int main()
{
	freopen ("ctc.in","r",stdin);
	freopen ("ctc.out","w",stdout);
	citire();
	conex();
	scrie();
	return 0;
}