#include<bits/stdc++.h>

using lld=long long;

const int N=2e5+5,M=2e5+5;

struct Edge{
    int to,nxt;
}e[M<<1];
int hd[N],pe=1;
void Add_Edge(int u,int v,bool T=true){
    e[++pe]={v,hd[u]},hd[u]=pe;
    if(T) Add_Edge(v,u,false);
}

int n,m;

int dfn[N],low[N],pdfn,stk[N],pstk;
bool instk[N];
std::vector<std::vector<int>> EBCC;
void DFS(int u,int fr){
    dfn[u]=low[u]=++pdfn;
    instk[stk[++pstk]=u]=true;
    for(int i=hd[u];i;i=e[i].nxt){
        int v=e[i].to;
        if(!dfn[v]) DFS(v,i),low[u]=std::min(low[u],low[v]);
        else if(i^fr^1) low[u]=std::min(low[u],dfn[v]);
    }
    if(dfn[u]==low[u]){
        EBCC.emplace_back();
        while(instk[u]){
            int top=stk[pstk--];
            instk[top]=false;
            EBCC.back().emplace_back(top);
        }
    }
}

int main(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;++i){
        int u,v; scanf("%d%d",&u,&v);
        Add_Edge(++u,++v);
    }
    for(int i=1;i<=n;++i) if(!dfn[i]) DFS(i,0);
    printf("%ld\n",EBCC.size());
    for(auto ebcc:EBCC){
        printf("%ld ",ebcc.size());
        for(int i=0;i<ebcc.size();++i) printf("%d%c",--ebcc[i]," \n"[i+1==ebcc.size()]);
    }
    return 0;
}