#include<cstdio>
#include<vector>
using namespace std;
int m,n,x,y,viz[100001],nr;
vector<int> a[100001],at[100001],b[100001],pord;
void citire()
{
	int i;
	scanf("%d%d", &n, &m);
	for(i=1;i<=m;i++)
	{
		scanf("%d%d",&x, &y);
		a[x].push_back(y);
		at[y].push_back(x);
	}
}
void DFS(int x)
{
	viz[x]=1;
	for(vector<int>::iterator it=a[x].begin();it!=a[x].end();it++)
		if(!viz[*it])
			DFS(*it);
	pord.push_back(x);
}
void DFST(int x)
{
	viz[x]=0;
	b[nr].push_back(x);
	for(vector<int>::iterator it=at[x].begin();it!=at[x].end();it++)
		if(viz[*it])
			DFST(*it);
}
int main()
{
	freopen("ctc.in","r",stdin);
	freopen("ctc.out","w",stdout);
	int i;
	citire();
	for(i=1;i<=n;i++)
		if(!viz[i])
			DFS(i);
	for(i=n-1;i>=0;i--)
		if(viz[pord[i]])
		{
			nr++;
			DFST(pord[i]);
		}
	printf("%d\n",nr);
	for(i=1;i<=nr;i++)
	{
		for(vector<int>::iterator it=b[i].begin(); it!=b[i].end(); it++)
			printf("%d ",*it);
		printf("\n");
	}
	return 0;
}