#include<fstream>
#include<vector>
using namespace std;
ifstream in("ctc.in");
ofstream out("ctc.out");
const int N=100010;
vector<int>a[N],at[N],coada[N];
int n,m,t,r,rez;
struct clar{int q,w;};
clar apa[N];
bool viz[N];
void read()
{
	int x,y;
	in>>n>>m;
	for(int i=1;i<=m;i++)
	{
		in>>x>>y;
		a[x].push_back(y);
		at[y].push_back(x);
	}
}
void dfs1(int x)
{
	viz[x]=1;
	t++;
	for(int i=0;i<a[x].size();i++)
		if(!viz[a[x][i]])
			dfs1(a[x][i]);
	r++;
	apa[r].q=x;
	apa[r].w=++t;
}
void dfs2(int x)
{
	viz[x]=1;
	coada[rez].push_back(x);
	for(int i=0;i<at[x].size();i++)
		if(!viz[at[x][i]])
			dfs2(at[x][i]);
}
void solve()
{
	for(int i=1;i<=n;i++)
		if(!viz[i])
			dfs1(i);
	for(int i=0;i<=n+1;i++)
		viz[i]=0;
	
	for(int i=r;i>=1;i--)
	{
		if(!viz[apa[i].q])
		{
			++rez;
			dfs2(apa[i].q);
		}
	}
}

void afis()
{
	out<<rez<<"\n";
	for(int i=1;i<=rez;i++)
	{
		for(int j=0;j<coada[i].size();j++)
			out<<coada[i][j]<<" ";
		out<<'\n';
	}
}
int main()
{
	read();
	solve();
	afis();
	return 0;
}