#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define fi first
#define se second
#define ps push_back
#define mk make_pair
const int N=1e6+10,inf=0x3f3f3f3f;
const ll linf=0x3f3f3f3f3f3f3f3f,mod=1e9+7;
inline ll read(){
	char c=getchar();ll x=0;bool f=0;
	while(!isdigit(c))f=c=='-'?1:0,c=getchar();
	while(isdigit(c))x=(x<<1)+(x<<3)+(c^48),c=getchar();
	return f?-x:x;
}
struct jj{
	int to,next;
}bi[N<<1];
int n,m,hd[N],cnt,tot,num,dfn[N],low[N],q[N],top,in[N];
inline void add(int x,int y){bi[++cnt]={y,hd[x]},hd[x]=cnt;}
vector<int> v[N];
bool vis[N];
inline void tarjan(int x,int f){
	dfn[x]=low[x]=++tot;vis[x]=1;q[++top]=x;
	for(int i=hd[x];i;i=bi[i].next){
		int j=bi[i].to;
		if(!dfn[j]){
			tarjan(j,x);low[x]=min(low[x],low[j]);
		}
		else if(vis[j])low[x]=min(low[x],dfn[j]);
	}
	if(dfn[x]==low[x]){
		int p;++num;
		do{
			p=q[top--];v[num].ps(p);vis[p]=0;
		}while(p!=x);
	}
}
signed main(){
	#ifndef ONLINE_JUDGE
	freopen("in.in","r",stdin);
	freopen("out.out","w",stdout);
	#endif

	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	n=read(),m=read();
	for(int i=1,x,y;i<=m;++i){
		x=read()+1,y=read()+1;add(x,y);
		++in[y];
	}
	for(int i=1;i<=n;++i){
		if(!in[i])tarjan(i,0);
	}
	for(int i=1;i<=n;++i)
		if(!dfn[i])tarjan(i,0);
	cout<<num<<'\n';
	for(int i=1;i<=num;++i){
		cout<<v[i].size()<<' ';
		for(auto j:v[i])
			cout<<j-1<<' ';
		cout<<'\n';
	}
}