# include <stdio.h>
# include <vector>

using namespace std;
vector <int> g[200010],g1[200010],vt[200010];

int i,x,n,y,nc,m,timp,st[200010],p,nr;
bool sel[200010];

void dfs(int x)
{
	sel[x]=true; 
	for (vector <int> :: iterator it=g[x].begin(); it!=g[x].end(); it++)
		if (sel[*it]==false)
			dfs(*it);
	st[++p]=x;
}

void dfs1(int x)
{
	vt[nr].push_back(x);
	sel[x]=true; 
	for (vector <int> :: iterator it=g1[x].begin(); it!=g1[x].end(); it++)
		if (sel[*it]==false)
			dfs1(*it);
}

int main()

{
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	scanf("%d %d\n",&n,&m);
	for (i=1; i<=m; i++)
	{
		scanf("%d %d\n",&x,&y);
		g[x].push_back(y);
		g1[y].push_back(x);
	}
	timp=0;
	for (i=1; i<=n; i++)
	if (sel[i]==false)
	{
		nc++;
		dfs(i);
	}
	for (i=1; i<=n; i++)
		sel[i]=false;
	for (i=n; i>=1; i--)
		if (sel[st[i]]==false)
		{
			nr++;
			dfs1(st[i]);
		}
	printf("%d\n",nr);
	for (i=1; i<=nr; i++)
	{
		for (vector <int> :: iterator it=vt[i].begin(); it!=vt[i].end(); it++)
			printf("%d ",*it);
		printf("\n");
	}
	return 0;
}