#include<bits/stdc++.h>

#define MAXN 1000010

using namespace std;

long long n, b;
struct stick
{
  long long h, p, i;
  bool operator< (stick other)
  {
      double f = (double)p / (double)h;
      double s = (double)other.p / (double)other.h;
      return f > s;
  }
}arr[MAXN];
long long ans[MAXN], cur = 1e18, k, penalty, knum, activeNum, activeLength[MAXN];
unsigned long long dif;
bool solution1 = false;
vector<long long> sz, szs;
vector<long long> podredba[MAXN];
mt19937 mt(chrono::high_resolution_clock::now().time_since_epoch().count());
std::chrono::high_resolution_clock::time_point beginOfTime;

long long rnd(int i)
{
    return mt() % i;
}
void read()
{
    ios_base::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 = 0; i < n; i ++)
    {
        cin>>arr[i].h;
        arr[i].i = i;
    }
    for(int i = 0; i < n; i ++)
    {
        cin>>arr[i].p;
    }
}
void solve(long long ttt)
{
    while(1)
    {
        auto bb = chrono::high_resolution_clock::now();
        if(chrono::duration_cast<chrono::milliseconds>(bb - beginOfTime).count() > ttt) break;
        int l = 0, done = 0;
        k = 0;
        penalty = 0;
        szs.clear();
        while(done < n)
        {
            int csz = 0;
            while(done < n && l + arr[done].h <= b)
            {
                l += arr[done].h;
                done ++;
                csz ++;
            }
            if(done < n && arr[done].p < dif && l != b)
            {
                l += arr[done].h;
                done ++;
                csz ++;
            }
            szs.push_back(csz);
            if(l > b)
            {
                penalty += arr[done - 1].p;
            }
            k ++;
            l = 0;
        }
        if(k * k * k + penalty < cur)
        {
            cur = k * k * k + penalty;
            for(int i = 0; i < n; i ++)
            {
                ans[i] = arr[i].i;
            }

            knum = k;
            sz = vector<long long>(szs);
        }
        random_shuffle(arr, arr + n, rnd);
    }
}
void proba()
{
    sort(arr, arr + n);
    activeNum = 0;
    int last = 0;
    for(int i = 0; i < n; i ++)
    {
        bool done = false;
        if(n - i <= activeNum)
        {
            last = i;
            break;
        }
        for(int j = 0; j <= activeNum; j ++)
        {
            if(activeLength[j] + arr[i].h < b)
            {
                activeLength[j] += arr[i].h;
                podredba[j].push_back(arr[i].i + 1);
                done = true;
                break;
            }
        }
        if(done == false)
        {
            activeLength[++activeNum] = arr[i].h;
            podredba[activeNum].push_back(arr[i].i + 1);
            if(arr[i].h > b) penalty += arr[i].p;
        }
    }
    for(int i = last; i < n; i ++)
    {
        bool done = false;
        for(int j = 0; j <= activeNum; j ++)
        {
            if(activeLength[j] < b)
            {
                activeLength[j] += arr[i].h;
                podredba[j].push_back(arr[i].i + 1);
                if(arr[i].h > b) penalty += arr[i].p;
                done = true;
                break;
            }
        }
        if(done == false)
        {
            activeLength[++activeNum] = arr[i].h;
            podredba[activeNum].push_back(arr[i].i + 1);
            if(arr[i].h > b) penalty += arr[i].p;
        }
    }
}
void print1()
{
    cout<<activeNum + 1<<'\n';
        for(int i = 0; i <= activeNum; i ++)
        {
            cout<<podredba[i].size();
            for(auto item : podredba[i])
            {
                cout<<" "<<item;
            }
            cout<<'\n';
        }
}
int main()
{
    read();
    dif = 1e18;
    int ttttt;
    if(n > 100000) ttttt = 4000;
    else if(n > 10000) ttttt = 4300;
    else ttttt = 4600;
    beginOfTime = chrono::high_resolution_clock::now();
    if(n < 600000)proba();
    solve(ttttt);
    if(activeNum * activeNum * activeNum + penalty <= cur && n < 500000)
    {
       print1();
    }
    else
    {
        cout<<knum<<'\n';
    int last = 0;
    for(int i = 0; i < sz.size(); i ++)
    {
        cout<<sz[i]<<" ";
        for(int j = 0; j < sz[i]; j ++)
        {
            cout<<ans[last ++] + 1<<" ";
        }
        cout<<'\n';
    }
    }

    return 0;
}
/*
8 12
1 5 8 12 6 7 9 3
0 1 2 3 4 5 6 7


4
3 8 6 4
3 5 2 1
1 7
1 3
*/