#include <iostream>
#include <fstream>
#include <cmath>
#include <vector>
#include <bitset>
#include <queue>
#include <deque>
#include <list>
#include <set>
#include <ctime>
#include <string>
#include <cstring>
#include <iomanip>
#include <algorithm>
using namespace std;
ifstream ff("ctc.in");
ofstream gg("ctc.out");
#define max 100001
vector<int> vv[max], qq;
vector<vector<int> > ll;
bool ww[max], ss[max];
int n, m, cc[max], zz[max], mm[max], k=1, p;

void trj(int x){
	int y;
	ww[x]=1;
	zz[x]=k;
	mm[x]=k;
	k++;
	cc[++p]=x;
	ss[x]=1;
	for(int i=0;i<(int)vv[x].size();i++){
		y=vv[x][i];
		if(!ww[y]){
			trj(y);
			mm[x]=min(mm[x], mm[y]);
		} else
		if(ss[y]){
			mm[x]=min(mm[x], mm[y]);
		}
	}
	if(mm[x]==zz[x]){
		qq.clear();
		do{
			y=cc[p--];
			ss[y]=0;
			qq.push_back(y);
		}while(y!=x);
		ll.push_back(qq);
	}
}

void sol(){
	for(int i=1;i<=n;i++)
	if(!ww[i]){
		trj(i);
	}
	gg << ll.size() << "\n";
	for(int i=0;i<(int)ll.size();i++){
	for(int j=0;j<(int)ll[i].size();j++) gg << ll[i][j] << " "; gg<<"\n"; } 
}

int main(){
	int a, b;
	ff >> n >> m;
	for(int i=0;i<m;i++){
		ff >> a >> b;
		vv[a].push_back(b);
	}
	sol();
}