#include <bits/stdc++.h>
using namespace std;
const int maxn = (int)2e5+5;
int n,m,idx,tag,dfn[maxn],fr[maxn],to[maxn],val[maxn],vis[maxn]; vector<int> f[maxn],ans[maxn];
void dfs(int u){
	dfn[u] = ++idx;
	for(auto X:f[u]){
		int nxt = fr[X]+to[X]-u;
		if(!dfn[nxt]) dfs(nxt), vis[X] = 1;
	}
}
void getans(int u,int pidx){
	dfn[u] = ++idx;
	for(auto X:f[u]){
		int nxt = fr[X]+to[X]-u;
		if(!dfn[nxt]) getans(nxt,X), val[u] += val[nxt];
	}
	if(val[u]==0) vis[pidx] = 2;
}
void search(int u){
	ans[tag].push_back(u);
	dfn[u] = ++idx;
	for(auto X:f[u])if(vis[X]==1){
		int nxt = fr[X]+to[X]-u;
		if(!dfn[nxt]) search(nxt);
	}
}
int main(){
	scanf("%d%d",&n,&m);
	for(int al=1;al<=m;al++)
		scanf("%d%d",&fr[al],&to[al]), ++fr[al], ++to[al], f[fr[al]].push_back(al), f[to[al]].push_back(al);
	for(int al=1;al<=n;al++)if(!dfn[al]) dfs(al);
	for(int al=1;al<=m;al++)if(!vis[al]){
		int A = fr[al], B = to[al];
		if(dfn[A]>dfn[B]) swap(A,B);
		--val[A], ++val[B];
	}
	for(int al=1;al<=n;al++) dfn[al] = 0;
	idx = 0;
	for(int al=1;al<=n;al++)if(!dfn[al]) getans(al,0);
	for(int al=1;al<=n;al++) dfn[al] = 0;
	idx = 0;
	for(int al=1;al<=n;al++)if(!dfn[al]) ++tag, search(al);
	printf("%d\n",tag);
	for(int al=1;al<=tag;al++,printf("\n")){
		printf("%d ",ans[al].size());
		for(auto X:ans[al]) printf("%d ",X-1);
	}
	return 0;
}