#include<bits/stdc++.h>
using namespace std;
const int N=1e6+10;
vector<int>scc[N],to[N];
int dfn[N],low[N],tt,in[N],cnt;
int sta[N],top;
void tarjan(int u)
{
	sta[++top]=u,in[u]=1;
	dfn[u]=++tt,low[u]=tt;
	for(int v:to[u])
		if(!dfn[v])tarjan(v),low[u]=min(low[u],low[v]);
		else if(in[v])low[u]=min(low[u],dfn[v]);
	if(dfn[u]==low[u])
	{
		int k;++cnt;
		do
		{
			k=sta[top--];in[k]=0;
			scc[cnt].push_back(k);
		}while(k!=u);
	}
}
int main()
{
	cin.tie(0)->sync_with_stdio(0);
	int n,m;cin>>n>>m;
	for(int i=1;i<=m;++i)
	{
		int u,v;cin>>u>>v;
		to[u].push_back(v);
	}
	for(int i=0;i<n;++i)
		if(!dfn[i])tarjan(i);
	cout<<cnt<<"\n";
	for(int i=1;i<=cnt;++i)
	{
		cout<<scc[i].size();
		for(int j:scc[i])cout<<" "<<j;cout<<"\n";
	}
}