#include<bits/stdc++.h>
using namespace std;

const int nmax=1e6+42;

int n;
long long b;

struct stick
{
    int id;
    int h;
    long long p;
};
stick inp[nmax],original_inp[nmax];

bool cmp(stick x,stick y)
{
    return x.h>y.h;
}

vector<int> outp[nmax];

set< pair<long long,int> > active;

long long best_score=2e18;

vector<int> out[nmax];

void print()
{
    int id=1;

    while(outp[id].size())id++;

    cerr<<best_score<<endl;

    printf("%i\n",id-1);

    for(int i=1;i<id;i++)
    {
        printf("%i",outp[i].size());

        for(auto w:outp[i])printf(" %i",w);
        printf("\n");
    }

    exit(0);
}

double T,bomb=4.5;

int go(int cnt_out)
{
    if(1.0*(clock()-T)/CLOCKS_PER_SEC>bomb)print();

    for(int i=1;i<=cnt_out;i++)
        out[i].push_back(inp[i].id);

    active={};

    int SZ=cnt_out;

    int id_total_smaller=0;
    int id_total_normal=cnt_out;

    if(b==1)id_total_smaller=cnt_out;

    for(int i=cnt_out+1;i<=n;i++)
    {
        set< pair<long long,int> > ::iterator it=active.lower_bound(make_pair(1LL*inp[i].h,0));

        pair<long long,int> val;

        if(it==active.end())
        {
            if(id_total_smaller<cnt_out&&inp[i].h!=b)
            {
                id_total_smaller++;
                val={b-1,id_total_smaller};
            }
            else
            {
                id_total_normal++;
                val={b,id_total_normal};
            }
        }

        else
        {
            val=(*it);
            active.erase(it);
        }

        out[val.second].push_back(inp[i].id);
        SZ=max(SZ,val.second);

        val.first-=inp[i].h;

        if(val.first>0)active.insert(val);
    }

    long long score=1LL*SZ*SZ*SZ;

    for(int i=1;i<=cnt_out;i++)
    {
        long long total_h=0;

        for(auto w:out[i])
            total_h+=original_inp[w].h;

        //cerr<<"i= "<<i<<" total_h= "<<total_h<<endl;

        if(total_h>b)
        {
            //cerr<<"out ";for(auto w:out[i])cerr<<w<<" ";cerr<<endl;

            int id_last=out[i][0];

            for(auto w:out[i])
                if(total_h-original_inp[w].h+1<=b&&original_inp[w].p<original_inp[id_last].p)
                    id_last=w;

            score+=original_inp[id_last].p;

            //cerr<<"i= "<<i<<" id_last= "<<id_last<<endl;

            for(int j=0;j<out[i].size();j++)
                if(out[i][j]==id_last)
                {
                    out[i].erase(out[i].begin()+j,out[i].begin()+j+1);
                    out[i].push_back(id_last);
                    break;
                }
        }
    }

    /*
    cerr<<cnt_out<<" has "<<SZ<<" "<<score<<endl;

    cerr<<"---"<<endl;
    */

    if(score<best_score)
    {
        best_score=score;

        for(int i=1;i<=n;i++)
            outp[i]={};

        for(int i=1;i<=SZ;i++)
            outp[i]=out[i];
    }

    for(int i=1;i<=SZ;i++)
        out[i]={};

    return SZ;
}

int main()
{
    freopen("sticks.in","r",stdin);
    freopen("sticks.out","w",stdout);

    T=clock();

    int cnt_out=0;

    scanf("%i%lld",&n,&b);

    for(int i=1;i<=n;i++)
    {
        inp[i].id=i;
        scanf("%i",&inp[i].h);

        if(inp[i].h>b)cnt_out++;
    }

    for(int i=1;i<=n;i++)
        scanf("%lld",&inp[i].p);

    for(int i=1;i<=n;i++)
        original_inp[i]=inp[i];

    sort(inp+1,inp+n+1,cmp);

    mt19937 rng(42);

    if(n>1e5)bomb=4.25;

    while(1)
    {
        go(cnt_out);
        go(n);

        int ok=n,not_ok=cnt_out;

        while(ok-not_ok>1)
        {
            int av=(ok+not_ok)/2;

            if(go(av)==av)ok=av;
            else not_ok=av;
        }

        shuffle(inp+cnt_out+1,inp+n+1,rng);
    }

    return 0;
}