#include<fstream>
#include<vector>
using namespace std;
FILE *g=fopen("ctc.out","w");

int i,j,n,m,viz[100002],t,ord[100002],x,y,cr=0,nr=0;
vector<int> a[100002];
vector<int> at[100002];
vector<int> d[100002];
void dfs(int x)
{
	int i;
	viz[x]=1;
	for(i=0;i<a[x].size();++i)
		if(!viz[a[x][i]])
			dfs(a[x][i]);
		ord[++cr]=x;
}
void dfst(int x)
{
	int i;
	viz[x]=0;
	d[nr].push_back(x);
	//fprintf(g,"%d ",x);
	for(i=0;i<at[x].size();++i)
		if(viz[at[x][i]])
		dfst(at[x][i]);
}
int main()
{
	FILE *f=fopen("ctc.in","r");
	fscanf(f,"%d%d",&n,&m);
	for(i=1;i<=m;++i)
	{
		fscanf(f,"%d%d",&x,&y);
		a[x].push_back(y);
		at[y].push_back(x);
	}
	for(i=1;i<=n;++i)
		if(!viz[i])
			dfs(i);
		for(i=n;i>=1;--i)
			if(viz[ord[i]])
			{
				++nr;
				dfst(ord[i]);
			}
			fprintf(g,"%d\n",nr);
			for(i=1;i<=nr;++i)
			{
				for(j=0;j<d[i].size();++j)
					fprintf(g,"%d ",d[i][j]);
				fprintf(g,"\n");
			}
	return 0;
}