#include <cstdio>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <algorithm>
#include <utility>
#include <string>
#include <functional>
#include <sstream>
#include <fstream>
#include <iostream>
using namespace std;
#define FOR(i,a,b) for (i=a;i<=b;i++)
#define fori(it,v) for (it=(v).begin();it!=(v).end();it++)
#define pb push_back
#define mp make_pair
#define fs first
#define ss second
#define all(c) c.begin(),c.end()
#define pf push_front
#define popb pop_back
#define popf pop_front
FILE *in,*out;
vector<int> ceva,a[100005];
vector<vector<int> > rez;
int mind[100005],b[100005],v[100005];
int nre;
stack<int> q;
void dfs(int x)
{	
	nre++;
	v[x]=nre;
	mind[x]=nre;	
	vector<int>::iterator it;
	q.push(x);
	b[x]=1;
	fori(it,a[x])
	{
		if (!v[*it])
		{
			dfs(*it);
			mind[x]=min(mind[x],mind[*it]);
			continue;
		}
		if (b[x])
		{
			mind[x]=min(mind[x],mind[*it]);
		}
	}
	if (v[x]!=mind[x])
		return ;
	ceva.clear();
	int aux;
	for(aux=q.top(),q.pop(),b[aux]=0,ceva.pb(aux);aux!=x;aux=q.top(),q.pop(),b[aux]=0,ceva.pb(aux)){}
	rez.pb(ceva);
}
int main()
{
	int n,m,i,x,y;
	in=fopen("ctc.in","r");
	out=fopen("ctc.out","w");
	fscanf(in,"%d%d",&n,&m);
	FOR(i,1,m)
	{
		fscanf(in,"%d%d",&x,&y);
		a[x].pb(y);
	}
	FOR(i,1,n)
		if (!v[i])
			dfs(i);
	fprintf(out,"%d\n",rez.size());
	vector< vector<int> >::iterator it;
	vector<int>::iterator jt;
	fori(it,rez)
	{
		fori(jt,*it)
			fprintf(out,"%d ",*jt);
		fprintf(out,"\n");
	}
	fclose(in);
	fclose(out);
	return 0;
}