#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <vector>
#define NMAX 100001
#define pb push_back
using namespace std;
int n,m,t,r,rez;
vector <int> G[NMAX],GT[NMAX],C[NMAX];
char viz[NMAX];
struct nod
{
	int a,b;
};
nod A[NMAX];
void read()
{
	scanf("%d%d",&n,&m);
	int x,y;
	while (m)
	{
		scanf("%d%d",&x,&y);
		G[x].pb(y);
		GT[y].pb(x);
		m--;
	}
}
void dfs1(int nod)
{
	viz[nod]=1;
	t++;
	int i;
	for (i=0; i<G[nod].size(); i++)
		if (!viz[G[nod][i]])
			dfs1(G[nod][i]);
	A[++r].a=nod; A[r].b=++t;
}
bool comp(nod x,nod y)
{
	if (x.b<y.b)
		return 1;
	return 0;
}
void dfs2(int nod)
{
	viz[nod]=1;
	int i;
	C[rez].pb(nod);
	for (i=0; i<GT[nod].size(); i++)
		if (!viz[GT[nod][i]])
			dfs2(GT[nod][i]);
}
void solve()
{
	int i;
	for (i=1; i<=n; i++)
		if (!viz[i])
			dfs1(i);
	sort(A+1,A+n+1,comp);
	memset(viz,0,sizeof(viz));
	for (i=n; i>=1; i--)
		if (!viz[A[i].a])
		{
			rez++;
			dfs2(A[i].a);
		}
}
void show()
{
	int i,j;
	printf("%d\n",rez);
	for (i=1; i<=rez; i++)
	{
		for (j=0; j<C[i].size(); j++)
			printf("%d ",C[i][j]);
		printf("\n");
	}
}
int main()
{
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	read();
	solve();
	show();
	return 0;
}