#include<iostream>
#include<vector>
#include<algorithm>
#include<climits>
#define MAXN 1000001
using namespace std;
long long b,pen1=0;
struct pruch{
    long long p;
    long long h;
    int ind;
};
struct dupka{
    long long currdep;
    vector<int> s;
};
bool cmp(pruch a,pruch b){
    if(a.p!=b.p) return a.p>b.p;
    return a.h<b.h;
}
bool cmp1(pruch a,pruch b){
    if(a.h!=b.h) return a.h>b.h;
    return a.p>b.p;
}
bool cmp2(pruch a,pruch b){
    if(a.h!=b.h) return a.h<b.h;
    return a.p>b.p;
}
int a[MAXN];
pruch stck[MAXN],stck1[MAXN];
dupka holes[MAXN],holes1[MAXN];
int n,dob[MAXN],inx[MAXN];
vector<int> valid;
int bsearch(long long val,int l,int r){
    int mid;
    while(l<r-1){
        mid=(l+r)/2;
        if(stck[valid[mid]].h<val) r=mid;
        else l=mid;
    }
    if(stck[valid[r]].h>val) return -1;
    return l;
}
long long currans=0,avgp=0;
bool used[MAXN];
long long cii;
int main(){
    srand(69);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    freopen("sticks.in","r",stdin);
    freopen("sticks.out","w",stdout);
    cin>>n>>b;
    for(int i=0;i<n;i++){
        cin>>stck[i].h;
        stck[i].ind=i+1;
        holes[i].currdep=b;
        holes1[i].currdep=b;
        inx[i]=i;
    }
    for(int i=0;i<n;i++){
        cin>>stck[i].p;
        avgp+=stck[i].h;
        stck1[i]=stck[i];
    }
    bool kvo=false;
    if(n<=10){
        vector<int> anss[MAXN];
        long long esth;
        esth=n*avgp/b;
        esth=3*esth*(esth-1)+1;
       // esth=esth/2*3;
        int ci,ansci=-1,br=0;
        currans=LLONG_MAX;
        do{
            ci=0;
            long long pen=0;
            for(int i0=0;i0<n;i0++){
                int i=inx[i0];
                if(holes[ci].currdep==0) ci++;
                if(stck[i].h>b){
                    holes[ci].s.push_back(stck[i].ind);
                    holes[ci].currdep=-1;
                    pen+=stck[i].p;
                    ci++;
                    continue;
                }
                if(holes[ci].currdep-stck[i].h<0){
                    if(stck[i].p<esth){
                        holes[ci].currdep-=stck[i].h;
                        holes[ci].s.push_back(stck[i].ind);
                        pen+=stck[i].p;
                        ci++;
                    }else{
                        ci++;
                        holes[ci].currdep-=stck[i].h;
                        holes[ci].s.push_back(stck[i].ind);
                    }
                }else{
                    holes[ci].currdep-=stck[i].h;
                    holes[ci].s.push_back(stck[i].ind);
                }
            }
            if(holes[ci].currdep!=b) ci++;
            long long ll=ci*ci*ci+pen;
            if(ll<currans){
            //cout<<currans<<" "<<ll<<"\n";
                currans=ll;
                ansci=ci;
                for(int i=0;i<ci;i++){
                    anss[i].clear();
                    for(int i1=0;i1<holes[i].s.size();i1++){
                        anss[i].push_back(holes[i].s[i1]);
                    }
                }
            }
            for(int i=0;i<ci;i++){
                holes[i].s.clear();
                holes[i].currdep=b;
            }
        }while(next_permutation(inx,inx+n));
        cout<<ansci<<"\n";
        for(int i=0;i<ansci;i++){
            cout<<anss[i].size()<<" ";
            for(int i1=0;i1<anss[i].size();i1++){
                cout<<anss[i][i1]<<" ";
            }
            cout<<"\n";
        }
        return 0;
    }
    if(!kvo){
        avgp/=n;
        int kol=0;
        long long esth;
        esth=n*avgp/b;
        esth=3*esth*(esth-1)+1;
        sort(stck,stck+n,cmp);
        esth=esth/5*3+10;
        for(int i=0;i<n;i++){
            if(stck[i].p<esth) break;
            valid.push_back(i);
            kol++;
        }
        //cout<<esth<<" "<<kol<<"\n";
      //  kol=min(n,kol+10);
        sort(stck,stck+kol,cmp1);
        //kol=0;
        long long pen=0;
        int brholes=0,vind=0;
        long long ci=0;
        for(int i=0;i<kol;i++){
            if(used[i]) continue;
            if(holes[ci].currdep==0) ci++;
            if(stck[i].h>b){
                holes[ci].s.push_back(stck[i].ind);
                holes[ci].currdep=-1;
                pen+=stck[i].p;
                ci++;
                used[i]=true;
                continue;
            }
            long long val=holes[ci].currdep;
            if(holes[ci].currdep-stck[i].h<0 && i!=kol-1 && vind!=valid.size()-1){
                int indd=bsearch(val,vind,valid.size()-1);
               // cout<<val<<" "<<indd<<"\n";
                while(indd!=-1){
                    if(stck[valid[indd]].h>val) indd++;
                    int in1=indd;
                    indd=valid[indd];
              //      cout<<"vlizam "<<valid.size()<<" "<<in1<<" "<<stck[indd].ind<<"\n";
                    used[indd]=true;
                    holes[ci].currdep-=stck[indd].h;
                    holes[ci].s.push_back(stck[indd].ind);
                    int sz=valid.size()-1;
                    swap(valid[in1],valid[sz]);
                    valid.pop_back();
                    for(int i1=in1+1;i1<sz;i1++){
                        swap(valid[i1],valid[i1-1]);
                    }
                    if(indd==kol-1 || in1==sz-1) break;
                    val=holes[ci].currdep;
                    indd=bsearch(val,in1,sz-1);
                }
                ci++;
            }
            holes[ci].currdep-=stck[i].h;
            used[i]=true;
            holes[ci].s.push_back(stck[i].ind);
            vind++;
        }
        for(int i=kol;i<n;i++){
            if(holes[ci].currdep==0) ci++;
            if(stck[i].h>b){
                holes[ci].s.push_back(stck[i].ind);
                holes[ci].currdep=-1;
                pen+=stck[i].p;
                ci++;
                continue;
            }
            if(holes[ci].currdep-stck[i].h<0) ci++;
            holes[ci].currdep-=stck[i].h;
            holes[ci].s.push_back(stck[i].ind);
        }
        if(holes[ci].currdep==b) ci--;
        ci++;
        currans=ci*ci*ci+pen;
        cii=ci;
        for(int i=ci-1;i>=0;i--){
            int ind=0,sz=holes[i].s.size();
            int naob=sz-1;
            bool krai=false;
            for(int i2=0;i2<ci;i2++){
                dob[i2]=0;
            }
            if(holes[i].currdep<0){
                pen-=stck1[holes[i].s[naob]-1].p;
            }
            for(int i1=0;i1<i;i1++){
                if(holes[i1].currdep<=0) continue;
              //  cout<<"vlazqm"<<"\n";
                int last;
                while(holes[i1].currdep>0){
                    if(ind>naob){
                       krai=true;
                       break;
                    }
                    int tempp1=holes[i].s[naob];
                    int tempp=holes[i].s[ind];
                /*    if(holes[i1].currdep-stck1[tempp1-1].h<0 && holes[i1].currdep-stck1[tempp-1].h<0){
                      //      cout<<"vlizam "<<tempp<<" "<<tempp1<<"\n";
                        tempp=tempp1;
                        naob--;
                        ind--;
                    }*/
                    holes[i1].currdep-=stck1[tempp-1].h;
                    last=tempp-1;
                    dob[i1]++;
                    holes[i1].s.push_back(tempp);
                    ind++;
                }
                if(krai) break;
                if(holes[i1].currdep<0) pen+=stck1[last].p;
            }
            cii--;
            krai=false;
            if(ind!=naob+1) krai=true;
            long long bruh=cii*cii*cii+pen;
            if(bruh<currans && !krai) currans=bruh;
            else krai=true;
          //  cout<<"vlizam "<<krai<<" "<<currans<<"\n";
            if(krai){
                for(int i1=0;i1<ci;i1++){
                    while(dob[i1]>0){
                        holes[i1].s.pop_back();
                        dob[i1]--;
                    }
                }
                cii++;
                break;
            }
        }
        //cout<<currans<<"\n";
    }
    //kvo=true;
    if(!kvo){
        sort(stck,stck+n,cmp1);
        int rind=0;
        long long ci=0;
        pen1=0;
        for(int i=n-1;i>=0;i--){
            if(i<rind) break;
            if(holes1[ci].currdep-stck[i].h<=0){
                holes1[ci].currdep-=stck[rind].h;
                holes1[ci].s.push_back(stck[rind].ind);
                if(holes1[ci].currdep<0) pen1+=stck1[stck[rind].ind-1].p;
                rind++;
                ci++;
            }
            if(i<rind) break;
            holes1[ci].currdep-=stck[i].h;
            holes1[ci].s.push_back(stck[i].ind);
            if(holes1[ci].currdep<=0){
                if(holes1[ci].currdep<0) pen1+=stck1[stck[i].ind-1].p;
                ci++;
            }
        }
        if(holes1[ci].currdep!=b){
            ci++;
        }
        pen1+=ci*ci*ci;
        if(n>1000){
       //    pen1*=5;
        }
        //cout<<pen1<<" "<<currans<<"\n";
        if(pen1<currans){
           // if(pen1>25000000000001) return 0;
            cii=ci;
            cout<<cii<<"\n";
            for(int i=0;i<cii;i++){
                cout<<holes1[i].s.size()<<" ";
                for(int i1=0;i1<holes1[i].s.size();i1++){
                    cout<<holes1[i].s[i1]<<" ";
                }
                cout<<"\n";
            }
            return 0;
        }
    }
        //return 0;
    cout<<cii<<"\n";
    for(int i=0;i<cii;i++){
        cout<<holes[i].s.size()<<" ";
        for(int i1=0;i1<holes[i].s.size();i1++){
            cout<<holes[i].s[i1]<<" ";
        }
        cout<<"\n";
    }
    return 0;
}