#include <stdio.h>
#include <string.h>
#include <vector>
#define NMAX 100005
#define pb push_back
using namespace std;
int n,m,A[NMAX],r,rez;
vector <int> G[NMAX],GT[NMAX],sol[NMAX];
char viz[NMAX];
void read()
{
	scanf("%d%d",&n,&m);
	int i,x,y;
	for (i=1; i<=m; i++)
	{
		scanf("%d%d",&x,&y);
		G[x].pb(y); GT[y].pb(x);
	}
}
void dfs(int nod)
{
	viz[nod]=1;
	int i,vec;
	for (i=0; i<G[nod].size(); i++)
	{
		vec=G[nod][i];
		if (!viz[vec])
			dfs(vec);
	}
	A[++r]=nod;
}
void dfs2(int nod)
{
	viz[nod]=1;   sol[rez].pb(nod);
	int i,vec;
	for (i=0; i<GT[nod].size(); i++)
	{
		vec=GT[nod][i];
		if (!viz[vec])
			dfs2(vec);
	}
}
void solve()
{
	int i,j;
	for (i=1; i<=n; i++)
		if (!viz[i])
			dfs(i);
	
	memset(viz,0,sizeof(viz));
	for (i=n; i>=1; i--)
		if (!viz[A[i]])
		{
			rez++;
			dfs2(A[i]);
		}
	printf("%d\n",rez);
	for (i=1; i<=rez; i++)
	{
		for (j=0; j<sol[i].size(); j++)
			printf("%d ",sol[i][j]);
		printf("\n");
	}
}
int main()
{
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	read();
	solve();
	return 0;
}