Problem: Valery is a PE teacher at a school in Berland. Soon the students are going to take a test in long jumps, and Valery has lost his favorite ruler! 

However, there is no reason for disappointment, as Valery has found another ruler, its length is l centimeters. The ruler already has n marks, with which he can make measurements. We assume that the marks are numbered from 1 to n in the order they appear from the beginning of the ruler to its end. The first point coincides with the beginning of the ruler and represents the origin. The last mark coincides with the end of the ruler, at distance l from the origin. This ruler can be repesented by an increasing sequence a1, a2, ..., an, where ai denotes the distance of the i-th mark from the origin (a1 = 0, an = l).

Valery believes that with a ruler he can measure the distance of d centimeters, if there is a pair of integers i and j (1 ≤ i ≤ j ≤ n), such that the distance between the i-th and the j-th mark is exactly equal to d (in other words, aj - ai = d). 

Under the rules, the girls should be able to jump at least x centimeters, and the boys should be able to jump at least y (x < y) centimeters. To test the children's abilities, Valery needs a ruler to measure each of the distances x and y. 

Your task is to determine what is the minimum number of additional marks you need to add on the ruler so that they can be used to measure the distances x and y. Valery can add the marks at any integer non-negative distance from the origin not exceeding the length of the ruler.

Input

The first line contains four positive space-separated integers n, l, x, y (2 ≤ n ≤ 105, 2 ≤ l ≤ 109, 1 ≤ x < y ≤ l) — the number of marks, the length of the ruler and the jump norms for girls and boys, correspondingly.

The second line contains a sequence of n integers a1, a2, ..., an (0 = a1 < a2 < ... < an = l), where ai shows the distance from the i-th mark to the origin.

Output

In the first line print a single non-negative integer v — the minimum number of marks that you need to add on the ruler.

In the second line print v space-separated integers p1, p2, ..., pv (0 ≤ pi ≤ l). Number pi means that the i-th mark should be at the distance of pi centimeters from the origin. Print the marks in any order. If there are multiple solutions, print any of them.

Examples

Input

3 250 185 230
0 185 250


Output

1
230


Input

4 250 185 230
0 20 185 250


Output

0


Input

2 300 185 230
0 300


Output

2
185 230

Note

In the first sample it is impossible to initially measure the distance of 230 centimeters. For that it is enough to add a 20 centimeter mark or a 230 centimeter mark.

In the second sample you already can use the ruler to measure the distances of 185 and 230 centimeters, so you don't have to add new marks.

In the third sample the ruler only contains the initial and the final marks. We will need to add two marks to be able to test the children's skills.

Solution (in JAVA):

Solution:

import java.io.*;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.StringTokenizer;

public class D {
    public static void main(String args[]) throws Exception {
        Reader reader = new Reader();
        reader.initConsoleReading();
        int n, l, x, y;
        n = reader.nextInt();
        l = reader.nextInt();
        x = reader.nextInt();
        y = reader.nextInt();
        boolean xFound, yFound;
        xFound = yFound = false;
        int[] marks = new int[n];
        HashSet<Integer> seen = new HashSet<>();
        HashSet<Integer> xNeed = new HashSet<>();
        for (int i = 0; i < n; i++) {
            marks[i] = reader.nextInt();
            if (seen.contains(marks[i] - x)) {
                xFound = true;
            }
            if (seen.contains(marks[i] - y)) {
                yFound = true;
            }
            xNeed.add(marks[i] + x);
            xNeed.add(marks[i] - x);
            seen.add(marks[i]);
        }
        if (xFound && yFound) {
            System.out.println(0);
        } else if (xFound) {
            System.out.println("1\n" + y);
        } else if (yFound) {
            System.out.println("1\n" + x);
        } else if (!make_1(xNeed, marks, y)) {
            System.out.println("2\n" + x + " " + y);
        }
        reader.dispose();

    }

    private static boolean make_1(HashSet<Integer> xNeed, int[] marks, int y) {
        int len = marks[marks.length - 1];
        for (int i = 0; i < marks.length; i++) {
            if (marks[i] + y <= len && xNeed.contains(marks[i] + y)) {
                System.out.println("1\n" + (marks[i] + y));
                return true;
            } else if (marks[i] - y >= 0 && xNeed.contains(marks[i] - y)) {
                System.out.println("1\n" + (marks[i] - y));
                return true;
            }
        }
        return false;
    }

    /************************************Helper Methods Begin Here**********************************************/
    private static String reverse(String toRev) {
        return new StringBuilder(toRev).reverse().toString();
    }

    public static class Pair<F extends Comparable<F>, S extends Comparable<S>> implements Comparable<Pair<F, S>> {
        static final int prime = 31;
        private F first;
        private S second;

        public Pair(F f, S s) {
            this.first = f;
            this.second = s;
        }

        @Override
        public int hashCode() {
            int result = 1;
            result = prime * result + this.first.hashCode();
            result = prime * result + this.second.hashCode();
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Pair<F, S> s = (Pair<F, S>) obj;
            return this.first.equals(s.first) && this.second.equals(s.second);
        }

        @Override
        public int compareTo(Pair<F, S> p) {
            int c1 = this.first.compareTo(p.first);
            if (c1 == 0) {
                return this.second.compareTo(p.second);
            }
            return c1;
        }
    }

    public static int swap(int a, int b) {
        /*a = Main.swap(b,b=a); goes from left to right*/
        return a;
    }

    public static long swap(long a, long b) {
        /*a = Main.swap(b,b=a); goes from left to right*/
        return a;
    }

    private static <T1, T2> void init6d(T1[][][][][][] sixD, T2 val) {
        for (T1[][][][][] fiveD : sixD) init5d(fiveD, val);
    }

    private static <T1, T2> void init5d(T1[][][][][] fiveD, T2 val) {
        for (T1[][][][] fourD : fiveD) init4d(fourD, val);
    }

    private static <T1, T2> void init4d(T1[][][][] fourD, T2 val) {
        for (T1[][][] threeD : fourD) init3d(threeD, val);
    }

    private static <T1, T2> void init3d(T1[][][] threeD, T2 val) {
        for (T1[][] twoD : threeD) init2d(twoD, val);
    }

    private static <T1, T2> void init2d(T1[][] twoD, T2 val) {
        for (T1[] oneD : twoD) init1d(oneD, val);
    }

    private static <T1, T2> void init1d(T1[] oneD, T2 val) {
        Arrays.fill(oneD, val);
    }

    public static boolean next_permutation(int[] p) {
        for (int a = p.length - 2; a >= 0; --a)
            if (p[a] < p[a + 1])
                for (int b = p.length - 1; ; --b)
                    if (p[b] > p[a]) {
                        int t = p[a];
                        p[a] = p[b];
                        p[b] = t;
                        for (++a, b = p.length - 1; a < b; ++a, --b) {
                            t = p[a];
                            p[a] = p[b];
                            p[b] = t;
                        }
                        return true;
                    }
        return false;
    }

    public static long gcd(long a, long b) {
        if (a < 0) a *= -1;
        if (b < 0) b *= -1;
        return b == 0 ? a : gcd(b, a % b);
    }

    public static class Reader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public Reader() {
        }

        public Reader initConsoleReading() {
            reader = new BufferedReader(new InputStreamReader(System.in), 32768);
            tokenizer = null;
            return this;
        }

        public Reader initFileReading(String filePath) throws FileNotFoundException {
            reader = new BufferedReader(new FileReader(filePath), 32768);
            tokenizer = null;
            return this;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public String nextLine() throws IOException {
            return reader.readLine();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public void dispose() throws IOException {
            this.reader.close();
        }
    }
    /************************************Helper Methods Ends Here**********************************************/
}