Problem: There are n students in a class working on group projects. The students will divide into groups (some students may be in groups alone), work on their independent pieces, and then discuss the results together. It takes the i-th student ai minutes to finish his/her independent piece.

If students work at different paces, it can be frustrating for the faster students and stressful for the slower ones. In particular, the imbalance of a group is defined as the maximum ai in the group minus the minimum ai in the group. Note that a group containing a single student has an imbalance of 0. How many ways are there for the students to divide into groups so that the total imbalance of all groups is at most k?

Two divisions are considered distinct if there exists a pair of students who work in the same group in one division but different groups in the other.

Input

The first line contains two space-separated integers n and k (1 ≤ n ≤ 200, 0 ≤ k ≤ 1000) — the number of students and the maximum total imbalance allowed, respectively.

The second line contains n space-separated integers ai (1 ≤ ai ≤ 500) — the time it takes the i-th student to complete his/her independent piece of work.

Output

Print a single integer, the number of ways the students can form groups. As the answer may be large, print its value modulo 109 + 7.

Examples

Input

3 2
2 4 5


Output

3


Input

4 3
7 8 9 10


Output

13


Input

4 0
5 10 20 21


Output

1

Note

In the first sample, we have three options: 

  * The first and second students form a group, and the third student forms a group. Total imbalance is 2 + 0 = 2. 
  * The first student forms a group, and the second and third students form a group. Total imbalance is 0 + 1 = 1. 
  * All three students form their own groups. Total imbalance is 0. 



In the third sample, the total imbalance must be 0, so each student must work individually.

Solution (in JAVA):

Solution:
import java.awt.Point;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Locale;
import java.util.Random;
import java.util.StringTokenizer;

import static java.lang.Math.max;
import static java.lang.Math.min;


public class CF626F implements Runnable{

    // SOLUTION AT THE TOP OF CODE!!!
    // HACK ME PLEASE IF YOU CAN!!!
    // PLEASE!!!
    // PLEASE!!!
    // PLEASE!!!

    @SuppressWarnings("unused")
    private final static Random rnd = new Random();
    private final static String fileName = "";

    private final static int MODULO = 1000 * 1000 * 1000 + 7;

    // THERE SOLUTION STARTS!!!
    private void solve() {
        int n = readInt();
        int maxAllowedSum = readInt();
        int[] a = readIntArray(n);

        long answer = getAnswer(n, a, maxAllowedSum);
        out.println(answer);
    }

    static long getAnswer(int n, int[] a, int maxAllowedSum) {
        Arrays.sort(a);

        int[] d = new int[n];
        for (int i = 1; i < n; ++i) {
            d[i] = a[i] - a[i - 1];
        }

        // cur, open, sum
        int[][][] dp = new int[2][n + 2][maxAllowedSum + 1];
        dp[0][0][0] = 1;

        final int[] emptyDp = new int[maxAllowedSum + 1];

        for (int cur = 0; cur < n; ++cur) {
            int[][] nextDp = dp[1 - cur % 2], curDp = dp[cur % 2];
            for (int[] nextRow : nextDp) {
                Arrays.fill(nextRow, 0);
            }

            int delta = d[cur];

            for (int curOpen = 0; curOpen <= n; ++curOpen) {
                int[] curOpenDp = curDp[curOpen];
                int sumDelta = delta * curOpen;

                int[] nextClosedDp = (0 == curOpen ? emptyDp : nextDp[curOpen - 1]);
                int[] nextContinueDp = nextDp[curOpen];
                int[] nextOpenDp = nextDp[curOpen + 1];

                for (int nextSum = sumDelta; nextSum <= maxAllowedSum; ++nextSum) {
                    int curDpValue = curOpenDp[nextSum - sumDelta];

                    // closing
                    nextClosedDp[nextSum] = add(
                            nextClosedDp[nextSum],
                            mult(curDpValue, curOpen)
                    );

                    // continue
                    nextContinueDp[nextSum] = add(
                            nextContinueDp[nextSum],
                            mult(curDpValue, curOpen + 1) // or join, or alone
                    );

                    // open
                    nextOpenDp[nextSum] = add(
                            nextOpenDp[nextSum],
                            curDpValue // curDpValue * 1
                    );
                }
            }
        }

        int answer = 0;
        int[] answerDp = dp[n % 2][0];
        for (int sum = 0; sum <= maxAllowedSum; ++sum) {
            answer = add(answer, answerDp[sum]);
        }

        return answer;
    }

    /////////////////////////////////////////////////////////////////////

    private final static boolean MULTIPLE_TESTS = true;
    private final boolean ONLINE_JUDGE = !new File("input.txt").exists();
//    private final boolean ONLINE_JUDGE = System.getProperty("ONLINE_JUDGE") != null;

    private final static int MAX_STACK_SIZE = 128;

    private final static boolean OPTIMIZE_READ_NUMBERS = true;

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private static long inverse(long x) {
        return binpow(x, MODULO - 2);
    }

    private static long binpow(long base, long power) {
        if (power == 0) return 1;
        if ((power & 1) == 0) {
            long half = binpow(base, power >> 1);
            return mult(half, half);
        } else {
            long prev = binpow(base, power - 1);
            return mult(prev, base);
        }
    }

    private static int add(int a, int b) {
        int result = a + b;
        if (result >= MODULO) result -= MODULO;
        return result;
    }

    @SuppressWarnings("unused")
    private static int subtract(int a, int b) { return add(a, MODULO - b % MODULO); }

    private static int mult(long a, long b) { return (int)((a * b) % MODULO); }

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    boolean yesNo(boolean yes) {
        out.println(yes ? "YES" : "NO");
        return yes;
    }

    /////////////////////////////////////////////////////////////////////

    public void run(){
        try{
            timeInit();
            Locale.setDefault(Locale.US);

            init();

            if (ONLINE_JUDGE) {
                solve();
            } else {
                do {
                    try {
                        timeInit();
                        solve();
                        time();

                        out.println();
                        out.flush();
                    } catch (NumberFormatException | EOFException e) {
                        break;
                    }
                } while (MULTIPLE_TESTS);
            }

            out.close();
            time();
        }catch (Exception e){
            e.printStackTrace(System.err);
            System.exit(-1);
        }
    }

    /////////////////////////////////////////////////////////////////////

    private BufferedReader in;
    private OutputWriter out;
    private StringTokenizer tok = new StringTokenizer("");

    public static void main(String[] args){
        new Thread(null, new CF626F(), "", MAX_STACK_SIZE * (1L << 20)).start();
    }

    /////////////////////////////////////////////////////////////////////

    private void init() throws FileNotFoundException{
        Locale.setDefault(Locale.US);

        if (ONLINE_JUDGE){
            if (fileName.isEmpty()) {
                in = new BufferedReader(new InputStreamReader(System.in));
                out = new OutputWriter(System.out);
            } else {
                in = new BufferedReader(new FileReader(fileName + ".in"));
                out = new OutputWriter(fileName + ".out");
            }
        }else{
            in = new BufferedReader(new FileReader("input.txt"));
            out = new OutputWriter("output.txt");
        }
    }

    ////////////////////////////////////////////////////////////////

    private long timeBegin;

    private void timeInit() {
        this.timeBegin = System.currentTimeMillis();
    }

    private void time(){
        long timeEnd = System.currentTimeMillis();
        System.err.println("Time = " + (timeEnd - timeBegin));
    }

    @SuppressWarnings("unused")
    private void debug(Object... objects){
        if (ONLINE_JUDGE){
            for (Object o: objects){
                System.err.println(o.toString());
            }
        }
    }

    /////////////////////////////////////////////////////////////////////

    private String delim = " ";

    private String readNullableLine() {
        try {
            return in.readLine();
        } catch (IOException e) {
            throw new RuntimeIOException(e);
        }
    }

    private String readLine() {
        String line = readNullableLine();
        if (null == line) throw new EOFException();
        return line;
    }

    private String readString() {
        while(!tok.hasMoreTokens()){
            tok = new StringTokenizer(readLine(), delim);
        }

        return tok.nextToken(delim);
    }

    /////////////////////////////////////////////////////////////////

    private final char NOT_A_SYMBOL = '\0';

    @SuppressWarnings("unused")
    private char readChar() {
        try {
            int intValue = in.read();

            if (intValue == -1){
                return NOT_A_SYMBOL;
            }

            return (char) intValue;
        } catch (IOException e) {
            throw new RuntimeIOException(e);
        }
    }

    private char[] readCharArray() {
        return readLine().toCharArray();
    }

    @SuppressWarnings("unused")
    private char[][] readCharField(int rowsCount) {
        char[][] field = new char[rowsCount][];
        for (int row = 0; row < rowsCount; ++row) {
            field[row] = readCharArray();
        }

        return field;
    }

    /////////////////////////////////////////////////////////////////

    private long optimizedReadLong() {
        int sign = 1;
        long result = 0;
        boolean started = false;
        while (true) {
            try {
                int j = in.read();
                if (-1 == j) {
                    if (started) return sign * result;
                    throw new NumberFormatException();
                }

                if (j == '-') {
                    if (started) throw new NumberFormatException();
                    sign = -sign;
                }

                if ('0' <= j && j <= '9') {
                    result = result * 10 + j - '0';
                    started = true;
                } else if (started) {
                    return sign * result;
                }
            } catch (IOException e) {
                throw new RuntimeIOException(e);
            }
        }
    }

    private int readInt() {

        if (!OPTIMIZE_READ_NUMBERS) {
            return Integer.parseInt(readString());
        } else {
            return (int) optimizedReadLong();
        }
    }

    private int[] readIntArray(int size) {
        int[] array = new int[size];

        for (int index = 0; index < size; ++index){
            array[index] = readInt();
        }

        return array;
    }

    @SuppressWarnings("unused")
    private int[] readSortedIntArray(int size) {
        Integer[] array = new Integer[size];

        for (int index = 0; index < size; ++index) {
            array[index] = readInt();
        }
        Arrays.sort(array);

        int[] sortedArray = new int[size];
        for (int index = 0; index < size; ++index) {
            sortedArray[index] = array[index];
        }

        return sortedArray;
    }

    private int[] readIntArrayWithDecrease(int size) {
        int[] array = readIntArray(size);

        for (int i = 0; i < size; ++i) {
            array[i]--;
        }

        return array;
    }

    ///////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private int[][] readIntMatrix(int rowsCount, int columnsCount) {
        int[][] matrix = new int[rowsCount][];

        for (int rowIndex = 0; rowIndex < rowsCount; ++rowIndex) {
            matrix[rowIndex] = readIntArray(columnsCount);
        }

        return matrix;
    }

    @SuppressWarnings("unused")
    private int[][] readIntMatrixWithDecrease(int rowsCount, int columnsCount) {
        int[][] matrix = new int[rowsCount][];

        for (int rowIndex = 0; rowIndex < rowsCount; ++rowIndex) {
            matrix[rowIndex] = readIntArrayWithDecrease(columnsCount);
        }

        return matrix;
    }

    ///////////////////////////////////////////////////////////////////

    private long readLong() {
        if (!OPTIMIZE_READ_NUMBERS) {
            return Long.parseLong(readString());
        } else {
            return optimizedReadLong();
        }
    }

    @SuppressWarnings("unused")
    private long[] readLongArray(int size) {
        long[] array = new long[size];

        for (int index = 0; index < size; ++index){
            array[index] = readLong();
        }

        return array;
    }

    ////////////////////////////////////////////////////////////////////

    private double readDouble() {
        return Double.parseDouble(readString());
    }

    @SuppressWarnings("unused")
    private double[] readDoubleArray(int size) {
        double[] array = new double[size];

        for (int index = 0; index < size; ++index){
            array[index] = readDouble();
        }

        return array;
    }

    ////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private BigInteger readBigInteger() {
        return new BigInteger(readString());
    }

    @SuppressWarnings("unused")
    private BigDecimal readBigDecimal() {
        return new BigDecimal(readString());
    }

    /////////////////////////////////////////////////////////////////////

    private Point readPoint() {
        int x = readInt();
        int y = readInt();
        return new Point(x, y);
    }

    @SuppressWarnings("unused")
    private Point[] readPointArray(int size) {
        Point[] array = new Point[size];

        for (int index = 0; index < size; ++index){
            array[index] = readPoint();
        }

        return array;
    }

    /////////////////////////////////////////////////////////////////////

    @Deprecated
    @SuppressWarnings("unused")
    private List<Integer>[] readGraph(int vertexNumber, int edgeNumber) {
        @SuppressWarnings("unchecked")
        List<Integer>[] graph = new List[vertexNumber];

        for (int index = 0; index < vertexNumber; ++index){
            graph[index] = new ArrayList<>();
        }

        while (edgeNumber-- > 0){
            int from = readInt() - 1;
            int to = readInt() - 1;

            graph[from].add(to);
            graph[to].add(from);
        }

        return graph;
    }

    private static class GraphBuilder {

        final int size;
        final List<Integer>[] edges;

        static GraphBuilder createInstance(int size) {
            @SuppressWarnings("unchecked")
            List<Integer>[] edges = new List[size];
            for (int v = 0; v < size; ++v) {
                edges[v] = new ArrayList<>();
            }

            return new GraphBuilder(edges);
        }

        private GraphBuilder(List<Integer>[] edges) {
            this.size = edges.length;
            this.edges = edges;
        }

        public void addEdge(int from, int to) {
            addDirectedEdge(from, to);
            addDirectedEdge(to, from);
        }

        public void addDirectedEdge(int from, int to) {
            edges[from].add(to);
        }

        public int[][] build() {
            int[][] graph = new int[size][];
            for (int v = 0; v < size; ++v) {
                List<Integer> vEdges = edges[v];
                graph[v] = castInt(vEdges);
            }

            return graph;
        }
    }

    @SuppressWarnings("unused")
    private final static int ZERO_INDEXATION = 0, ONE_INDEXATION = 1;

    @SuppressWarnings("unused")
    private int[][] readUnweightedGraph(int vertexNumber, int edgesNumber) {
        return readUnweightedGraph(vertexNumber, edgesNumber, ONE_INDEXATION, false);
    }

    private int[][] readUnweightedGraph(int vertexNumber, int edgesNumber,
                                        int indexation, boolean directed
    ) {
        GraphBuilder graphBuilder = GraphBuilder.createInstance(vertexNumber);
        for (int i = 0; i < edgesNumber; ++i) {
            int from = readInt() - indexation;
            int to = readInt() - indexation;

            if (directed) graphBuilder.addDirectedEdge(from, to);
            else graphBuilder.addEdge(from, to);
        }

        return graphBuilder.build();
    }

    private static class Edge {
        int to;
        int w;

        Edge(int to, int w) {
            this.to = to;
            this.w = w;
        }
    }

    @SuppressWarnings("unused")
    private Edge[][] readWeightedGraph(int vertexNumber, int edgesNumber) {
        return readWeightedGraph(vertexNumber, edgesNumber, ONE_INDEXATION, false);
    }

    private Edge[][] readWeightedGraph(int vertexNumber, int edgesNumber,
                                       int indexation, boolean directed) {
        @SuppressWarnings("unchecked")
        List<Edge>[] graph = new List[vertexNumber];
        for (int v = 0; v < vertexNumber; ++v) {
            graph[v] = new ArrayList<>();
        }

        while (edgesNumber --> 0) {
            int from = readInt() - indexation;
            int to = readInt() - indexation;
            int w = readInt();

            graph[from].add(new Edge(to, w));
            if (!directed) graph[to].add(new Edge(from, w));
        }

        Edge[][] graphArrays = new Edge[vertexNumber][];
        for (int v = 0; v < vertexNumber; ++v) {
            graphArrays[v] = graph[v].toArray(new Edge[0]);
        }

        return graphArrays;
    }

    /////////////////////////////////////////////////////////////////////

    private static class IntIndexPair {

        @SuppressWarnings("unused")
        static Comparator<IntIndexPair> increaseComparator = (indexPair1, indexPair2) -> {
            int value1 = indexPair1.value;
            int value2 = indexPair2.value;

            if (value1 != value2) {
                return value1 - value2;
            }

            int index1 = indexPair1.index;
            int index2 = indexPair2.index;

            return index1 - index2;
        };

        @SuppressWarnings("unused")
        static Comparator<IntIndexPair> decreaseComparator = (indexPair1, indexPair2) -> {
            int value1 = indexPair1.value;
            int value2 = indexPair2.value;

            if (value1 != value2) {
                return -(value1 - value2);
            }

            int index1 = indexPair1.index;
            int index2 = indexPair2.index;

            return index1 - index2;
        };

        @SuppressWarnings("unused")
        static IntIndexPair[] from(int[] array) {
            IntIndexPair[] iip = new IntIndexPair[array.length];
            for (int i = 0; i < array.length; ++i) {
                iip[i] = new IntIndexPair(array[i], i);
            }

            return iip;
        }

        int value, index;

        IntIndexPair(int value, int index) {
            super();
            this.value = value;
            this.index = index;
        }

        @SuppressWarnings("unused")
        int getRealIndex() {
            return index + 1;
        }
    }

    @SuppressWarnings("unused")
    private IntIndexPair[] readIntIndexArray(int size) {
        IntIndexPair[] array = new IntIndexPair[size];

        for (int index = 0; index < size; ++index) {
            array[index] = new IntIndexPair(readInt(), index);
        }

        return array;
    }

    /////////////////////////////////////////////////////////////////////

    private static class OutputWriter extends PrintWriter {

        final int DEFAULT_PRECISION = 12;

        private int precision;
        private String format, formatWithSpace;

        {
            precision = DEFAULT_PRECISION;

            format = createFormat(precision);
            formatWithSpace = format + " ";
        }

        OutputWriter(OutputStream out) {
            super(out);
        }

        OutputWriter(String fileName) throws FileNotFoundException {
            super(fileName);
        }

        int getPrecision() {
            return precision;
        }

        void setPrecision(int precision) {
            precision = max(0, precision);
            this.precision = precision;

            format = createFormat(precision);
            formatWithSpace = format + " ";
        }

        String createFormat(int precision){
            return "%." + precision + "f";
        }

        @Override
        public void print(double d){
            printf(format, d);
        }
        
        @Override
        public void println(double d){
            print(d);
            println();
        }

        void printWithSpace(double d){
            printf(formatWithSpace, d);
        }

        void printAll(double...d){
            for (int i = 0; i < d.length - 1; ++i){
                printWithSpace(d[i]);
            }

            print(d[d.length - 1]);
        }

        @SuppressWarnings("unused")
        void printlnAll(double... d){
            printAll(d);
            println();
        }
        
        void printAll(int... array) {
        	for (int value : array) {
        		print(value + " ");
        	}
        }

        @SuppressWarnings("unused")
        void printlnAll(int... array) {
        	printAll(array);
        	println();
        }
        
        void printAll(long... array) {
        	for (long value : array) {
        		print(value + " ");
        	}
        }

        @SuppressWarnings("unused")
        void printlnAll(long... array) {
        	printAll(array);
        	println();
        }
    }

    /////////////////////////////////////////////////////////////////////

    private static class EOFException extends RuntimeException {

        EOFException() {
            super();
        }
    }

    private static class RuntimeIOException extends RuntimeException {

        /**
         *
         */
        private static final long serialVersionUID = -6463830523020118289L;

        RuntimeIOException(Throwable cause) {
            super(cause);
        }
    }

    /////////////////////////////////////////////////////////////////////
    //////////////// Some useful constants andTo functions ////////////////
    /////////////////////////////////////////////////////////////////////

    private static void swap(int[] array, int i, int j) {
        if (i != j) {
            int tmp = array[i];
            array[i] = array[j];
            array[j] = tmp;
        }
    }

    private static <T> void swap(T[] array, int i, int j) {
        if (i != j) {
            T tmp = array[i];
            array[i] = array[j];
            array[j] = tmp;
        }
    }

    private static final int[][] steps = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    private static final int[][] steps8 = {
            {-1, 0}, {1, 0}, {0, -1}, {0, 1},
            {-1, -1}, {1, 1}, {1, -1}, {-1, 1}
    };

    @SuppressWarnings("unused")
    private static boolean checkCell(int row, int rowsCount, int column, int columnsCount) {
        return checkIndex(row, rowsCount) && checkIndex(column, columnsCount);
    }

    private static boolean checkIndex(int index, int lim){
        return (0 <= index && index < lim);
    }

    /////////////////////////////////////////////////////////////////////

    private static int getBit(long mask, int bit) { return (int)((mask >> bit) & 1); }

    @SuppressWarnings("unused")
    private static boolean checkBit(long mask, int bit){
        return getBit(mask, bit) != 0;
    }

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private static long getSum(int[] array) {
        long sum = 0;
        for (int value: array) {
            sum += value;
        }

        return sum;
    }

    @SuppressWarnings("unused")
    private static long getSum(long[] array) {
        long sum = 0;
        for (long value: array) {
            sum += value;
        }

        return sum;
    }

    @SuppressWarnings("unused")
    private static Point getMinMax(int[] array) {
        int min = array[0];
        int max = array[0];

        for (int index = 0, size = array.length; index < size; ++index, ++index) {
            int value = array[index];

            if (index == size - 1) {
                min = min(min, value);
                max = max(max, value);
            } else {
                int otherValue = array[index + 1];

                if (value <= otherValue) {
                    min = min(min, value);
                    max = max(max, otherValue);
                } else {
                    min = min(min, otherValue);
                    max = max(max, value);
                }
            }
        }

        return new Point(min, max);
    }

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private static boolean isPrime(int x) {
        if (x < 2) return false;
        for (int d = 2; d * d <= x; ++d) {
            if (x % d == 0) return false;
        }

        return true;
    }

    @SuppressWarnings("unused")
    private static int[] getPrimes(int n) {
        boolean[] used = new boolean[n];
        used[0] = used[1] = true;

        int size = 0;
        for (int i = 2; i < n; ++i) {
            if (!used[i]) {
                ++size;
                for (int j = 2 * i; j < n; j += i) {
                    used[j] = true;
                }
            }
        }

        int[] primes = new int[size];
        for (int i = 0, cur = 0; i < n; ++i) {
            if (!used[i]) {
                primes[cur++] = i;
            }
        }

        return primes;
    }

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    int[] getDivisors(int value) {
        List<Integer> divisors = new ArrayList<>();
        for (int divisor = 1; divisor * divisor <= value; ++divisor) {
            if (value % divisor == 0) {
                divisors.add(divisor);
                if (divisor * divisor != value) {
                    divisors.add(value / divisor);
                }
            }
        }

        return castInt(divisors);
    }

    @SuppressWarnings("unused")
    long[] getDivisors(long value) {
        List<Long> divisors = new ArrayList<>();
        for (long divisor = 1; divisor * divisor <= value; ++divisor) {
            if (value % divisor == 0) {
                divisors.add(divisor);
                if (divisor * divisor != value) {
                    divisors.add(value / divisor);
                }
            }
        }

        return castLong(divisors);
    }

    /////////////////////////////////////////////////////////////////////

    @SuppressWarnings("unused")
    private static long lcm(long a, long b) {
        return a / gcd(a, b) * b;
    }

    private static long gcd(long a, long b) {
        return (a == 0 ? b : gcd(b % a, a));
    }

    /////////////////////////////////////////////////////////////////////

    private static int[] castInt(List<Integer> list) {
        int[] array = new int[list.size()];
        for (int i = 0; i < array.length; ++i) {
            array[i] = list.get(i);
        }

        return array;
    }

    @SuppressWarnings("unused")
    private static long[] castLong(List<Long> list) {
        long[] array = new long[list.size()];
        for (int i = 0; i < array.length; ++i) {
            array[i] = list.get(i);
        }

        return array;
    }

    /////////////////////////////////////////////////////////////////////

    /**
     * Generates list with keys 0..<bowlsCount
     * @param n - exclusive limit of sequence
     */
    @SuppressWarnings("unused")
    private static List<Integer> order(int n) {
        List<Integer> sequence = new ArrayList<>();
        for (int i = 0; i < n; ++i) {
            sequence.add(i);
        }

        return sequence;
    }

    @SuppressWarnings("unused")
    private static List<Integer> shuffled(List<Integer> list) {
        Collections.shuffle(list, rnd);
        return list;
    }
}