#include<bits/stdc++.h>
#define endl '\n'
#define fi first
#define se second

using namespace std;

const int MAXN=1e6+5;

struct Stick
{
    long long h,p;
    int num;
};

int n;
long long b;
Stick st[MAXN];
vector<int> hl[MAXN];
long long s[MAXN];
priority_queue<pair<long long,int> > pq;
long long ptr=0;

bool cmp(Stick a,Stick b)
{
    if(a.p==b.p) return a.h>b.h;
    return a.p>b.p;
}

int main()
{
ios::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);

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

cin>>n>>b;
for(int i=1;i<=n;i++) cin>>st[i].h;
for(int i=1;i<=n;i++) cin>>st[i].p;
for(int i=1;i<=n;i++) st[i].num=i;

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

pq.push({b,++ptr});
for(int i=1;i<=n;i++)
{
    if(pq.empty())
    {
        hl[++ptr].push_back(i);
        pq.push({b-st[i].h, ptr});
        continue;
    }
    auto cur=pq.top();//cout<<cur.fi<<" "<<cur.se<<endl;
    pq.pop();
    if(cur.fi<=0)
    {
        hl[++ptr].push_back(i);
        pq.push({b-st[i].h, ptr});
        continue;
    }
    hl[cur.se].push_back(i);
    if(st[i].h<cur.fi) pq.push({cur.fi-st[i].h, cur.se});
}
while(!pq.empty()) pq.pop();

for(int i=1;i<=ptr;i++)
{
    for(auto x: hl[i]) s[i]+=st[x].h;
    if(s[i]<b) pq.push({b-s[i],i});
}

for(int it=0;it<10;it++)
{
    for(int i=1;i<=ptr;i++)
    {
        if(hl[i].size()<2) continue;
        if(s[i]<=b) continue;
        long long curp=st[hl[i].back()].p;
        long long curh=st[hl[i].back()].h;
        if(!pq.empty())
        {
            auto cur=pq.top();
            if(curh<=cur.fi)
            {
                hl[cur.se].push_back(hl[i].back());
                hl[i].pop_back();
                pq.pop();
                s[cur.se]+=curh;
                if(s[cur.se]<b) pq.push({b-s[cur.se],cur.se});
                s[i]-=curh;
                pq.push({b-s[i],i});
                continue;
            }
        }
        long long up=(ptr+1)*(ptr+1)*(ptr+1)-ptr*ptr*ptr;
        if(curp>up)
        {
            hl[++ptr].push_back(hl[i].back());
            hl[i].pop_back();
            s[i]-=curh;
            pq.push({b-s[i],i});
        }
    }
}

cout<<ptr<<endl;
for(int i=1;i<=ptr;i++)
{
    cout<<hl[i].size()<<" ";
    for(int j=0;j<hl[i].size();j++) cout<<st[hl[i][j]].num<<" ";
    cout<<endl;
}

return 0;
}