#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
#define pb push_back 
const int N=1e5+3;
int n,m,tim,tot,top,dfn[N],low[N],col[N],sta[N];
vector<int>ve[N],ans[N];
void Dfs(int x)
{
	low[x]=dfn[x]=++tim;sta[++top]=x;
	for(int y:ve[x])
	{
		if(dfn[y]){if(!col[y])low[x]=min(low[x],dfn[y]);continue;}
		Dfs(y);low[x]=min(low[x],low[y]);
	}
	if(dfn[x]==low[x])for(tot++;sta[top+1]!=x;top--)col[sta[top]]=tot;
}
int main()
{
	cin>>n>>m;
	for(int i=1,x,y;i<=m;i++)
		cin>>x>>y,ve[++x].push_back(++y);
	for(int i=1;i<=n;i++)if(!dfn[i])Dfs(i);
	cout<<tot<<endl;
	for(int i=1;i<=n;i++)ans[col[i]].pb(i);
	for(int i=1;i<=tot;i++,cout<<endl)
	{
		cout<<ans[i].size()<<" ";
		for(int x:ans[i])cout<<x-1<<" ";
	}
}