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 a_1, a_2, ..., a_{n}, where a_{i} denotes the distance of the i-th mark from the origin (a_1 = 0, a_{n} = 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, a_{j} - a_{i} = 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 ≤ 10^5, 2 ≤ l ≤ 10^9, 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 a_1, a_2, ..., a_{n} (0 = a_1 < a_2 < ... < a_{n} = l), where a_{i} 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 p_1, p_2, ..., p_{v} (0 ≤ p_{i} ≤ l). Number p_{i} means that the i-th mark should be at the distance of p_{i} 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.

Difficulty: interview

Starter code:

Solutions:
import itertools
import math

def can_measure(a, d):
	return any(i + d in a for i in a)

def main():
	n, l, x, y = list(map(int, input().split()))
	a = set(map(int, input().split()))
	
	can_x = can_measure(a, x)
	can_y = can_measure(a, y)
	if can_x and can_y:
		print(0)
	elif can_x:
		print(1)
		print(y)
	elif can_y:
		print(1)
		print(x)
	else:
		for i in a:
			if i + x + y in a:
				print(1)
				print(i + x)
				break
			else:
				t = i + x - y in a
				if 0 <= i + x <= l and t:
					print(1)
					print(i + x)
					break;
				if 0 <= i - y <= l and t:
					print(1)
					print(i - y)
					break;
				
		else:
			print(2)
			print(x, y)
		

def __starting_point():
	main()

__starting_point()

import sys

first = sys.stdin.readline().split(" ")
n = int(first[0])
l = int(first[1])
x = int(first[2])
y = int(first[3])
second = sys.stdin.readline().split(" ")

have_dict = {}
need_dict_x = {}
need_dict_y = {}

for val in second:
	have_dict[val] = 1
	val = int(val)
	need_dict_x[str(val - x)] = 1
	need_dict_x[str(val+x)] = 1
	need_dict_y[str(val - y)] = 1
	need_dict_y[str(val + y)] = 1


need_x = 1
need_y = 1
something = 1
for val in have_dict.keys():
	try:
		need_dict_x[val]
		need_x = 0
	except:
		something += 1
	try: 
		need_dict_y[val]
		need_y = 0
	except:
		something -= 1
need_vals = []
if need_x == 1 and need_y == 1:
	to_return = 2
	return_val = str(x) + " "+str(y)
	for val in need_dict_x.keys():
		if int(val) < 0 or int(val) > l: 
			continue
		else:
			try: 
				need_dict_y[val]
				to_return = 1
				return_val = val
			except:
				continue
	print(to_return)
	print(return_val)
else:	
	print(need_x+need_y)
	if need_x == 1:
		print(x)
	elif need_y == 1:
		print(y)

n, l, x, y = list(map(int, input().split()))
a = set(map(int, input().split()))
ok1 = ok2 = ok3 = False
for c in a:
    if c + x in a:
        ok1 = True
    if c + y in a:
        ok2 = True
    if c - x > 0 and c - x + y in a:
        ok3 = True
        mark = c - x
    if c + x < l and c + x - y in a:
        ok3 = True
        mark = c + x
    if c + x + y in a:
        ok3 = True
        mark = c + x    
    if c - x - y in a:
        ok3 = True
        mark = c - x
if ok1 and ok2:
    print(0)
elif (not ok1) and (not ok2):    
    if ok3:
        print(1)
        print(mark)
    else:
        print(2)
        print(x, y)
else:
    print(1)
    print(y if ok1 else x)




#Adapted from code of hatsuyuki15 in this contest
n, l, x, y = list(map(int, input().split()))
a = set(map(int, input().split()))
boy = False
girl = False
one = False
where = -1
for i in a:
    if i + x in a:
        boy = True
    if i + y in a:
        girl = True
    if i - x > 0 and i - x + y in a:
        one = True
        where = i - x
    if i + x < l and i + x - y in a:
        one = True
        where = i + x
    if i + x + y in a:
        one = True
        where = i + x
    if i - x - y in a:
        one = True
        where = i - x


if boy and girl:
    print(0)
if boy and not girl:
    print(1)
    print(y)
if girl and not boy:
    print(1)
    print(x)
if not boy and not girl:
    if one:
        print(1)
        print(where)
    if not one:
        print(2)
        print(x, y)


#Adapted from code of hatsuyuki15 in this contest
n, l, x, y = map(int, input().split())
a = set(map(int, input().split()))
boy = False
girl = False
one = False
where = -1
for i in a:
    if i + x in a:
        boy = True
    if i + y in a:
        girl = True
    if i - x > 0 and i - x + y in a:
        one = True
        where = i - x
    if i + x < l and i + x - y in a:
        one = True
        where = i + x
    if i + x + y in a:
        one = True
        where = i + x


if boy and girl:
    print(0)
if boy and not girl:
    print(1)
    print(y)
if girl and not boy:
    print(1)
    print(x)
if not boy and not girl:
    if one:
        print(1)
        print(where)
    if not one:
        print(2)
        print(x, y)

__author__ = "zabidon"

n, l, x, y = map(int, input().split())
data = set(map(int, input().split()))

old_x = any(i + x in data for i in data)
old_y = any(i + y in data for i in data)

if old_x and old_y:
    #all
    print(0)
elif old_x:
    #one
    print(1)
    print(y)
elif old_y:
    #one
    print(1)
    print(x)
else:
    found = False
    for i in data:
        if i + x + y in data:
            found = True
            print(1)
            print(i + x)

        elif i + x - y in data:
            # because x<y
            # i + x - y mean exist one mark
            if 0 <= i + x <= l:
                found = True
                print(1)
                print(i + x)

            if not found and 0 <= i - y <= l:
                found = True
                print(1)
                print(i - y)
        if found:
            break
     
    if not found:
        print(2)
        print(x, y)

a = input().split(' ')
b = input().split(' ')
n=int(a[1])
x=int(a[2])
y=int(a[3])
xcan=False
ycan=False
xycan=False
xymoar=False
cool=0
cool2=0
s=set()
for element in b:
    s.add(int(element))
for c in s:
    if c+x in s:
        xcan=True
    if c+y in s:
        ycan=True
    if c+x+y in s:
        xycan = True
        cool=c
    if c+y-x in s:
        if c+y>n:
            if c-x<0:
                pass
            else:
                cool2 = c-x
                xymoar=True
        else:
            xymoar = True
            cool2 = c+y
    if xcan:
        if ycan:
            break
if xcan==True:
    if ycan==True:
        result=0
        marks=[]
    else:
        result = 1
        marks=[y]
else:
    if ycan == True:
        result = 1
        marks=[x]
    else:
        if xycan == True:
            result=1
            marks=[cool+x]
        elif xymoar == True:
            result=1
            marks=[cool2]
        else:
            result=2
            marks=[x,y]
print(result)
for i in range(len(marks)):
    print(marks[i], end=' ')

#!/usr/bin/env python3

def rl(T=str):
    return list(map(T,input().split()))

def ok(a,d,x):
    for v in a:
        if v+x in d:
            return True
    return False


def try_one(a,d,x,y):
    def can_place(v):
        #print(v)
        #print(v+x,v-x,v+y,v-y)
        if a[0] <= v <= a[-1]:
            if (v + x in d or v - x in d) and \
               (v + y in d or v - y in d):
               return True

        return False;
    for v in a:
        for _ in [-x,+x,-y,+y]:
            if can_place(v+_):
                return v+_;

    return None

def main():
    n, l, x, y = rl(int)
    a = rl(int)
    d = set(a)

    if ok(a,d,x):
        if ok(a,d,y):
            print(0)
        else:
            print(1)
            print(y)
    else:
        if ok(a,d,y):
            print(1)
            print(x)
        else:
            p = try_one(a,d,x,y)
            if p is not None:
                print(1)
                print(p)
            else:
                print(2)
                print(x,y)

main()


n, l, x, y = map(int, input().split())

def f(t, q):
    i = j = 0
    while j < n:
        d = t[j] - t[i]
        if d < q: j += 1
        elif d > q: i += 1
        else: return 0
    return q

def g(t):
    q = x + y
    i = j = 0
    while j < n:
        d = t[j] - t[i]
        if d < q: j += 1
        elif d > q: i += 1
        else: return t[j]
    return 0

def h(t):
    q = y - x
    i = j = 0
    while j < n:
        d = t[j] - t[i]
        if d < q: j += 1
        elif d > q: i += 1
        else:
            a, b = t[i] - x, t[j] + x
            if a >= 0: return [a]
            if b <= l:return [b]
            j += 1
    return [x, y]

def e(t):
    print(len(t))
    print(' '.join(map(str, t)))

t = list(map(int, input().split()))
t.sort()
x = f(t, x)
y = f(t, y)
if x and y:
    z = g(t)
    if z: e([z - y])
    else: e(h(t))
elif x: e([x])
elif y: e([y])
else: e([])

n, l, x, y = map(int, input().split())
s = set(map(int, input().split()))

def f(d): return any(i + d in s for i in s)
def g():
    for i in s:
        if i + x + y in s: return i + x
    return 0
def h():
    for i in s:
        if i + y - x in s:
            if i - x >= 0: return i - x
            if i + y <= l: return i + y
    return 0

def e(d):
    print(1)
    print(d)

if f(x):
    if f(y): print(0)
    else: e(y)
elif f(y): e(x)
else:
    z = g()
    if z: e(z)
    else:
        z = h()
        if z: e(z)
        else:
            print(2)
            print(x, y)

def main():
    import sys
    
    tokens = [int(i) for i in sys.stdin.read().split()]
    tokens.reverse()
    
    n, l, x, y = [tokens.pop() for i in range(4)]
    marks = set(tokens)
    
    x_index = y_index = sum_index = sub_index1 = sub_index2 = -1
    for i in marks:
        if i + x in marks:
            x_index = y
        if i + y in marks:
            y_index = x
        if i + x + y in marks:
            sum_index = i + x
        if i + y - x in marks and i - x >= 0:
            sub_index1 = i - x
        if i + y - x in marks and i + y <= l:
            sub_index2 = i + y
    
    if x_index != -1 and y_index != -1:
        print(0)
    else:
        for i in (x_index, y_index, sum_index, sub_index1, sub_index2):
            if i != -1:
                print(1)
                print(i)
                break
        else:
            print(2)
            print(x, y)
    
    
main()


def main():
    import sys
    
    tokens = [int(i) for i in sys.stdin.read().split()]
    tokens.reverse()
    
    n, l, x, y = [tokens.pop() for i in range(4)]
    marks = set(tokens)
    
    flag_x = flag_y = False
    index = -1
    for i in marks:
        if i + x in marks:
            flag_x = True
            index = y
        if i + y in marks:
            flag_y = True
            index = x
        if i + x + y in marks:
            index = i + x
        if i + y - x in marks and i - x >= 0:
            index = i - x
        if i + y - x in marks and i + y <= l:
            index = i + y
    
    if flag_x and flag_y:
        print(0)
    elif index != -1:
        print(1)
        print(index)
    else:
        print(2)
        print(x, y)
    
    
main()


def main():
    from bisect import bisect_left
    n, l, x, y = list(map(int, input().split()))
    aa, d = list(map(int, input().split())), {}
    for z in (x, y, y + x):
        for a in aa:
            a += z
            if a > l:
                break
            b = aa[bisect_left(aa, a)]
            if b <= a:
                if b == a:
                    d[z] = a
                break
        if len(d) == 2:
            break
    if d:
        if x in d and y in d:
            res = []
        elif x in d:
            res = [y]
        elif y in d:
            res = [x]
        elif y + x in d:
            res = [d[y + x] - y]
    else:
        z, tmp = y - x, []
        for a in aa:
            a += z
            if a > l:
                break
            b = aa[bisect_left(aa, a)]
            if b == a:
                tmp.append(a)
        for a in tmp:
            if a > y:
                res = [a - y]
                break
            elif a + x < l:
                res = [a + x]
                break
        else:
            res = [x, y]
    print(len(res))
    if res:
        print(*res)


def __starting_point():
    main()

__starting_point()

R = lambda: map(int, input().split())
n, l, x, y = R()
arr = set(R())
x_good, y_good = False, False
for m in arr:
    if m + x in arr or m - x in arr:
        x_good = True
        break
for m in arr:
    if m + y in arr or m - y in arr:
        y_good = True
        break
if x_good and y_good:
    print(0)
    return
elif x_good:
    print(1)
    print(y)
    return
elif y_good:
    print(1)
    print(x)
    return
else:
    for m in arr:
        if m + x <= l and (m + x + y in arr or m + x - y in arr):
            print(1)
            print(m + x)
            return
        if m - x >= 0 and (m - x + y in arr or m - x - y in arr):
            print(1)
            print(m - x)
            return
        if m + y <= l and (m + y + x in arr or m + y - x in arr):
            print(1)
            print(m + y)
            return
        if m - y >= 0 and (m - y + x in arr or m - y - x in arr):
            print(1)
            print(m - y)
            return
print(2)
print(x, y)

from collections import defaultdict as dc
def serch(a,b,x,y):
        for i in range(1,n):
                if (b[a[i]-x-y]):
                        return a[i]-y
                if b[a[i]-(y-x)] and a[i]+x<=l:
                        return a[i]+x
                if b[a[i]+(y-x)] and a[i]-x>=0:
                        return a[i]-x
        return 0
                
n,l,x,y=[int(i) for i in input().split()]
a=[int(i) for i in input().split()]
b=dc(int)
b=dc(lambda :0,b)
k1=0
k2=0
for i in range(n):
        b[a[i]]=1
        if b[a[i]-x]==1:
                k1=1
        if b[a[i]-y]==1:
                k2=1
if k1==1 and k2==1:
        print(0)
elif k1==0 and k2==0:
        z=serch(a,b,x,y)
        if z!=0:
                print(1)
                print(z)
        else:
                print(2)
                print(x,y)
elif k1==0:
        print(1)
        print(x)
else:
        print(1)
        print(y)



                



import itertools
import math

def can_measure(a, d):
	return any(i + d in a for i in a)

def main():
	n, l, x, y = list(map(int, input().split()))
	a = set(map(int, input().split()))
	
	can_x = can_measure(a, x)
	can_y = can_measure(a, y)
	if can_x and can_y:
		print(0)
	elif can_x:
		print(1)
		print(y)
	elif can_y:
		print(1)
		print(x)
	else:
		for i in a:
			if i + x + y in a:
				print(1)
				print(i + x)
				break
			else:
				t = i + x - y in a
				if 0 <= i + x <= l and t:
					print(1)
					print(i + x)
					break;
				if 0 <= i - y <= l and t:
					print(1)
					print(i - y)
					break;
				
		else:
			print(2)
			print(x, y)
		

def __starting_point():
	main()
        
        
            


        

        
        
            




__starting_point()

from collections import defaultdict

class LongJumps():
    def __init__(self, n, l, x, y, a):
        self.n, self.l, self.x, self.y, self.a = n,l,x,y,a

    def get_markers(self):
        st = defaultdict(set)
        req_pts = [self.x,self.y]
        exist_check = defaultdict(bool)
        value_check = defaultdict(bool)
        for v in self.a:
            exist_check[v] = True

        for v in self.a:
            for i in range(len(req_pts)):
                if v - req_pts[i] >= 0:
                    st[v - req_pts[i]].add(i)
                    if exist_check[v - req_pts[i]]:
                        value_check[i] = True
                if v + req_pts[i] <= l:
                    st[v+req_pts[i]].add(i)
                    if exist_check[v + req_pts[i]]:
                        value_check[i] = True

        if value_check[0] and value_check[1]:
            print(0)
            return

        sol_status = 2
        status1_marker = None
        for v in st:
            if len(st[v]) == 2:
                sol_status = 1
                status1_marker = v
            elif len(st[v]) == 1:
                if exist_check[v]:
                    sol_status = 1
                    status1_marker = req_pts[1-st[v].pop()]
        
        if sol_status == 1:
            print(1)
            print(status1_marker)
            return
        else:
            print(2)
            print(x, y)

n, l, x, y = list(map(int,input().strip(' ').split(' ')))
a = list(map(int,input().strip(' ').split(' ')))
lj = LongJumps(n,l,x,y,a)
lj.get_markers()

def main():
    n,l,x,y = list(map(int,input().split()))
    arr = set(map(int,input().split()))
    first = False
    second = False
    for i in arr:
        if i+x in arr:
            first = True
        if i+y in arr:
            second = True

    if first and not second:
        print(1)
        print(y)
        return
    if second and not first:
        print(1)
        print(x)
        return
    if first and second:
        print(0)
        return

    found = False
    for i in arr:
        if i+x-y in arr and i+x <= l:
            found = True
            coord = i+x
            break

        if i+y-x in arr and i+y <= l:
            found = True
            coord = i+y
            break

        if i+x+y in arr and i+min(x,y) <= l:
            found = True
            coord = i+min(x,y)

        if i-x-y in arr and i-max(x,y) >= 0:
            found = True
            coord = i-max(x,y)

        if i-x+y in arr and i-x >= 0:
            found = True
            coord = i-x
            break

        if i-y+x in arr and i-y >= 0:
            found = True
            coord = i-y
            break

        if found:
            break

    if found:
        print(1)
        print(coord)
        return

    print(2)
    print(x,y)


main()


# -*- coding: utf-8 -*-

import math
import collections
import bisect
import heapq
import time
import random
import itertools
import sys
from typing import List

"""
created by shhuan at 2020/1/13 20:48

"""


def solve(N, L, X, Y, A):
    vs = set(A)
    mx = any([a+X in vs for a in A])
    my = any([a+Y in vs for a in A])
    if mx and my:
        print(0)
    elif mx:
        print(1)
        print(Y)
    elif my:
        print(1)
        print(X)
    else:
        # try to add 1 mark
        for a in vs:
            for b, c in [(a + X, Y), (a + Y, X), (a - X, Y), (a - Y, X)]:
                if 0 <= b <= L:
                    if (b + c <= L and b + c in vs) or (b - c >= 0 and b - c in vs):
                        print(1)
                        print(b)
                        return

        # add 2 marks
        print(2)
        print('{} {}'.format(X, Y))


N, L, X, Y = map(int, input().split())
A = [int(x) for x in input().split()]
solve(N, L, X, Y, A)

import itertools
import math
 
def can_measure(a, d):
	return any(i + d in a for i in a)
 
def main():
	n, l, x, y = map(int, input().split())
	a = set(map(int, input().split()))
	
	can_x = can_measure(a, x)
	can_y = can_measure(a, y)
	if can_x and can_y:
		print(0)
	elif can_x:
		print(1)
		print(y)
	elif can_y:
		print(1)
		print(x)
	else:
		for i in a:
			if i + x + y in a:
				print(1)
				print(i + x)
				break
			else:
				t = i + x - y in a
				if 0 <= i + x <= l and t:
					print(1)
					print(i + x)
					break;
				if 0 <= i - y <= l and t:
					print(1)
					print(i - y)
					break;
				
		else:
			print(2)
			print(x, y)
		
 
def __starting_point():
	main()
__starting_point()

def __starting_point():	
	n, l, x, y = list(map(int, input().split()))
	v = list(map(int, input().split()))
	s = set(v)

	cx = 0
	for i in range(n):
		if v[i]+x in s:
			cx = 1
			break
	
	cy = 0
	for i in range(n):
		if v[i]+y in s:
			cy = 1
			break
	
	count = 0
	ans = []

	if cx==0:
		count += 1
		ans.append(x)
	if cy==0:
		count += 1
		ans.append(y)

	if count==2:
		for i in range(n):
			if (v[i]+x+y in s):
				count = 1
				ans = [v[i]+x]
				break

	if count==2:
		for i in range(n):
			if (v[i]+x-y in s):
				if v[i]+x<=l:
					count = 1
					ans = [v[i]+x]
					break
				elif v[i]-y>=0:
					count = 1
					ans = [v[i]-y]
					break

	print(count)
	if count!=0:
		print(*ans)

__starting_point()

n,l,x,y=list(map(int,input().split(" ")))
li=list(map(int,input().split(" ",n)[:n]))
li.sort()
dic={}
a1,a2=0,0
ans=2
x1=x
y1=y
xi=-1
yi=-1
for i in li:
    dic[i]=1
for i in range(n):
    if li[i]-x>=0:
        if li[i]-x in dic:
            a1=1
            xi=i
    if li[i]+x<=l:
        if li[i]+x in dic:
            a1=1
            xi=i
    if li[i]-y>=0:
        if li[i]-y in dic:
            a2=1
            yi=i
    if li[i]+y<=l:
        if li[i]+y in dic:
            a2=1
            yi=i
if a1==1 and a2==1:
    print(0)
elif a1==1:
    if li[xi]-x>=0:
        if li[xi]-x in dic:
            if li[xi]-x+y<=l and li[xi]-x+y in dic:
                a2=1
            if li[xi]-x-y>=0 and li[xi]-x-y in dic:
                a2=1
    if li[xi]+x<=l:
        if li[xi]+x in dic:
            if li[xi]+x+y<=l and li[xi]+x+y in dic:
                a2=1
            if li[xi]+x-y>=0 and li[xi]+x-y in dic:
                a2=1
    if a2==1:
        print(0)
    else:
        print(1)
        print(y)
elif a2==1:
    if li[yi]-y>=0:
        if li[yi]-y in dic:
            if li[yi]-y+x<=l and li[yi]-y+x in dic:
                a1=1
            if li[yi]-y-x>=0 and li[yi]-y-x in dic:
                a1=1
    if li[yi]+y<=l:
        if li[yi]+x in dic:
            if li[yi]+y+x<=l and li[yi]+y+x in dic:
                a1=1
            if li[yi]+y-x>=0 and li[yi]+y-x in dic:
                a1=1
    if a1==1:
        print(0)
    else:
        print(1)
        print(x)
else:
    for i in range(n):
        if li[i]-x>=0:
            a1=1
            xi=i
            if li[xi]-x+y<=l and li[xi]-x+y in dic:
                a2=1
            if li[xi]-x-y>=0 and li[xi]-x-y in dic:
                a2=1
            if a2==1:
                print(1)
                print(li[i]-x)
                break
            else:
                a1=0
        if li[i]+x<=l:
            a1=1
            xi=i
            if li[xi]+x+y<=l and li[xi]+x+y in dic:
                a2=1
            if li[xi]+x-y>=0 and li[xi]+x-y in dic:
                a2=1
            if a2==1:
                print(1)
                print(li[i]+x)
                break
            else:
                a1=0
        if li[i]-y>=0:
            a2=1
            yi=i
            if li[yi]-y+x<=l and li[yi]-y+x in dic:
                a1=1
            if li[yi]-y-x>=0 and li[yi]-y-x in dic:
                a1=1
            if a1==1:
                print(1)
                print(li[i]-y)
                break
            else:
                a2=0
        if li[i]+y<=l:
            a2=1
            yi=i
            if li[yi]+y+x<=l and li[yi]+y+x in dic:
                a1=1
            if li[yi]+y-x>=0 and li[yi]+y-x in dic:
                a1=1
            if a1==1:
                print(1)
                print(li[i]+y)
                break
            else:
                a2=0
if a1==0 and a2==0:
    print(2)
    print(x,y)


n, l, x, y = map(int, input().split())
s = set(map(int, input().split()))


def f(d): return any(i + d in s for i in s)


def g():
    for i in s:
        if i + x + y in s: return i + x
    return 0


def h():
    for i in s:
        if i + y - x in s:
            if i - x >= 0: return i - x
            if i + y <= l: return i + y
    return 0


def e(d):
    print(1)
    print(d)


if f(x):
    if f(y):
        print(0)
    else:
        e(y)
elif f(y):
    e(x)
else:
    z = g()
    if z:
        e(z)
    else:
        z = h()
        if z:
            e(z)
        else:
            print(2)
            print(x, y)