#include <bits/stdc++.h>
#define LL long long
#define sl(n) strlen(n)
#define endline puts("")
#define pii pair<int , int>
#define pr_q priority_queue
#define debug puts("DEBUG.")
using namespace std;
const int N = 5e5 + 10;
const int inf = ~0u >> 2;
int n,m;
struct edge
{
	int v,w,nxt;
}e[N];
int hd[N],cnt = 1;
void add(int u , int v)
{
	++cnt,e[cnt].v = v;
	e[cnt].nxt = hd[u],hd[u] = cnt;
}
int dfn[N],dfn_t,low[N];
int st[N],top,tot;
vector<int> vc[N];
bool vis[N];
void dfs(int u)
{
	st[++top] = u,vis[u] = 1;
	dfn[u] = low[u] = ++dfn_t;
	bool fl = 0;
	for(int i = hd[u];i;i = e[i].nxt)
	{
		int v = e[i].v;
		if( vis[v] )
			low[u] = min(low[u] , dfn[v] );
		else if(!dfn[v] )
		{
			dfs(v);
			low[u] = min(low[u] , low[v] );
		}
	}
	if(low[u] == dfn[u] )
	{
		++tot;
		int v;
		do
		{
			v = st[top--],vis[v] = 0;
			vc[tot].push_back(v);
		}while(v != u);
	}
}
int main()
{
	cin >> n >> m;
	for(int i = 1,u,v;i <= m;i++)
	{
		scanf("%d%d" , &u , &v),++u,++v;
		if(u == v)
			continue;
		add(u , v);
	}
	for(int i = 1;i <= n;i++)
		if( !dfn[i] )
			dfs(i);
	cout << tot << endl;
	for(int i = tot;i;i--,endline)
	{
		printf( "%d " , vc[i].size() );
		for(int x : vc[i] )
			printf("%d " , x - 1);
	}
	return 0;
}