using namespace std;
#include<iostream>
#include<cstdio>
#include<vector>
#define MAX 100005
struct nod{
    int info;
    nod *next;
};

nod *G[MAX], *Gt[MAX];
vector<int> ct[MAX];
int n,ord[MAX],timp,v[MAX],vt[MAX],NR[MAX],nr,nrc;

void citire()
{
    int i,m,a,b;
    nod *p;
    scanf("%d%d", &n, &m);
    for(i=1;i<=n;i++)
        G[i]=Gt[i]=NULL;
    for(i=1;i<=m;i++)
    {
        scanf("%d%d", &a, &b);
        p=new nod;
        p->info=b;
        p->next=G[a];
        G[a]=p;
        p=new nod;
        p->info=a;
        p->next=Gt[b];
        Gt[b]=p;
    }
}

void dfs(int varf)
{
    v[varf]=1;
    for(nod *p=G[varf];p;p=p->next)
        if(v[p->info]==0)
            dfs(p->info);
    ord[++timp]=varf;
}


void dfst(int varf,int nrc)
{
    nod *p;
    vt[varf]=nrc;
    ct[nrc].push_back(varf);
    //sort(nrc);
    for(p=Gt[varf]; p ; p=p->next)
        if(vt[p->info]==0)
            dfst(p->info,nrc);
}

void kosaraju()
{
    int i;
    for(i=1;i<=n;i++)
        if(v[i]==0)
            dfs(i);
    for(i=timp;i>0;i--)
        if(vt[ord[i]]==0)
            dfst(ord[i],++nrc);
}

void write2()
{
    printf("%d\n",nrc);
    int i,j,nr;
    for(i=1;i<=nrc;i++)
    {
        nr=ct[i].size();
        printf("%d ", nr);
        for(j=0;j<nr;j++)
            printf("%d ", ct[i][j]);
        printf("\n");
    }
}

void Afis(nod *G[]){
    for(int i=1;i<=n;++i){
        printf("%d : ",i);
        for(nod *p=G[i]; p ; p=p->next)
            printf("%d ",p->info);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    kosaraju();
    write2();
    return 0;
}