#include <cstdio>
#include <vector>
using namespace std;
vector <int> graf[100003];
vector <int> grafinv[100003];
vector <int> tarec[100003];
vector <int> stiva;
int n,m,cnt,vizitat[100003];
void dfs (int nod)
{
	vizitat[nod]=1;stiva.push_back(nod);
	for(int i=0;i<(int)graf[nod].size();++i)
		if(vizitat[graf[nod][i]]==0)
			dfs(graf[nod][i]);
}
void dfs1 (int nod)
{
	vizitat[nod]=0;tarec[cnt].push_back(nod);
	for(int i=0;i<(int)grafinv[nod].size();++i)
		if(vizitat[grafinv[nod][i]]==1)
			dfs1(grafinv[nod][i]);
}
void ctc_kosaraju ()
{
	for(int i=1;i<=n;++i)
		if(vizitat[i]==0)
			dfs(i);
	while(stiva.size()!=0)
	{
		if(vizitat[stiva[stiva.size()-1]]==1)
			dfs1(stiva[stiva.size()-1]),++cnt;
		stiva.pop_back();
	}
}
int main ()
{
	int nr1,nr2;
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	scanf("%d%d", &n, &m);
	for(int i=1;i<=m;++i)
	{
		scanf("%d%d", &nr1, &nr2);
		graf[nr1].push_back(nr2);grafinv[nr2].push_back(nr1);
	}
	ctc_kosaraju();
	printf("%d\n", cnt);
	for(int i=0;i<cnt;++i)
	{
		for(int i1=0;i1<(int)tarec[i].size();++i1)
			printf("%d ", tarec[i][i1]);
		printf("\n");
	}
	return 0;
}