#include <fstream>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <time.h>

using namespace std;

int partition(float arr[], int arrId[], int start, int end) {
    float pivot = arr[start];
 
    int count = 0;
    for (int i = start + 1; i <= end; i++) {
        if (arr[i] <= pivot)
            count++;
    }

    int pivotIndex = start + count;
    swap(arr[pivotIndex], arr[start]);
	swap(arrId[pivotIndex], arrId[start]);
 
    // Sorting left and right parts of the pivot element
    int i = start, j = end;
 
    while (i < pivotIndex && j > pivotIndex) {
 
        while (arr[i] > pivot) {
            i++;
        }
 
        while (arr[j] <= pivot) {
            j--;
        }
 
        if (i < pivotIndex && j > pivotIndex) {
            swap(arr[i], arr[j]);
			swap(arrId[i++], arrId[j--]);
        }
    }
 
    return pivotIndex;
}

void quickSort(float arr[], int arrId[], int start, int end) {
    if (start >= end) return;
 
    int p = partition(arr, arrId, start, end);

    quickSort(arr, arrId, start, p - 1);
    quickSort(arr, arrId, p + 1, end);
}

int main()
{
	ifstream inp;
	inp.open("sticks.in");
	
	int n;
	long long b;
	inp>>n>>b;
	
	int* h = new int[n];
	long long* p = new long long[n];
	
	for (int i = 0; i < n; ++i) {
		inp>>h[i];
	}
	for (int i = 0; i < n; ++i) {
		inp>>p[i];
	}
	inp.close();
	//cout<<1<<endl;
	
	float* ph = new float[n];
	int* phId = new int[n];
	for (int i = 0; i < n; ++i) {
		float phValue = (float)p[i]/h[i];
		ph[i] = phValue;
		phId[i] = i;
	}
	
	/*for (int i = 0; i < n-1; ++i) {
		for (int j = i+1; j < n; ++j) {
			if (ph[i]<ph[j]) {
				float t1 = ph[i];
				ph[i] = ph[j];
				ph[j] = t1;
				int t2 = phId[i];
				phId[i] = phId[j];
				phId[j] = t2;
			}
		}
	}*/
	/*for (int i = 0; i < n; ++i) {
		cout<<ph[i]<<" ";
	}
	cout<<endl;*/
	quickSort(ph,phId,0,n-1);
	/*for (int i = 0; i < n; ++i) {
		cout<<ph[i]<<" ";
	}
	cout<<endl;*/
	
	int k = 0;
	int* d = new int[n];
	int** s = new int*[n];
	int bb = 0;
	int* sk = new int[n];
	d[0] = 0;
	int ii = n;
	for (int i = 0; i < ii; ++i) { // when ii-- i must i-- also
		if (bb + h[phId[i]] + 1 >= b) {
			//cout<<2<<" "<<k<<endl;
			ii--;
			i--;
			sk[d[k]++] = phId[ii]+1;
			bb += h[phId[ii]];
						
			s[k] = new int[d[k]];
			for (int a = 0; a < d[k]; ++a) {
				s[k][a] = sk[a];
			}
			k++;
			d[k] = 0;
			bb = 0;
		} else {
			//cout<<3<<" "<<k<<endl;
			sk[d[k]++] = phId[i]+1;
			bb += h[phId[i]];
		}
	}
	s[k]= sk;
	k++;
	if (d[k-1] == 0) k--;
	
	ofstream out;
	out.open("sticks.out");
	
	out<<k<<endl;
	for (int i = 0; i < k; ++i) {
		out<<d[i];
		for (int j = 0; j < d[i]; ++j) {
			out<<" "<<s[i][j];
		}
		out<<endl;
	}
	
	/* 
	out<<n<<endl;
	for (int i = 0; i < n; ++i) {
		out<<1<<" "<<i+1<<endl;
	}
	*/
	
	out.close();
	
	return 0;
}