//#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>

using namespace std;

int use[100005];
int st[100005];

vector <int> g[100005];
vector <int> gt[100005];
vector <int> ctc[100005];
int sol=0;

void dfs(int nod)
{
	use[nod]=1;
	for(int i=0;i<g[nod].size();++i)
		if(!use[g[nod][i]]) dfs(g[nod][i]);

	st[++st[0]]=nod;
}

void dfst(int nod)
{
	use[nod]=1;
	for(int i=0;i<gt[nod].size();++i)
		if(!use[gt[nod][i]]) dfst(gt[nod][i]);

	ctc[sol].push_back(nod);
}

int main()
{
    ifstream cin("ctc.in");
    ofstream cout("ctc.out");
	int n,m,x,y;

    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
	memset(st,0,sizeof(st));
	memset(use,0,sizeof(use));
	for(int i=1;i<=n;++i)
		if(!use[i])
            dfs(i);
	memset(use,0,sizeof(use));
	for(int i=n;i>0;--i)
		if(!use[st[i]]){
		sol++;
		dfst(st[i]);
	}

	cout<<sol<<"\n";
	for(int i=1;i<=sol;++i){
		for(int j=0;j<ctc[i].size();j++)
			cout<<ctc[i][j]<<" ";
		cout<<"\n";
	}
	return 0;
}