Eugeny has n cards, each of them has exactly one integer written on it. Eugeny wants to exchange some cards with Nikolay so that the number of even integers on his cards would equal the number of odd integers, and that all these numbers would be distinct. 

Nikolay has m cards, distinct numbers from 1 to m are written on them, one per card. It means that Nikolay has exactly one card with number 1, exactly one card with number 2 and so on. 

A single exchange is a process in which Eugeny gives one card to Nikolay and takes another one from those Nikolay has. Your task is to find the minimum number of card exchanges and determine which cards Eugeny should exchange.


-----Input-----

The first line contains two integers n and m (2 ≤ n ≤ 2·10^5, 1 ≤ m ≤ 10^9) — the number of cards Eugeny has and the number of cards Nikolay has. It is guaranteed that n is even.

The second line contains a sequence of n positive integers a_1, a_2, ..., a_{n} (1 ≤ a_{i} ≤ 10^9) — the numbers on Eugeny's cards.


-----Output-----

If there is no answer, print -1.

Otherwise, in the first line print the minimum number of exchanges. In the second line print n integers — Eugeny's cards after all the exchanges with Nikolay. The order of cards should coincide with the card's order in the input data. If the i-th card wasn't exchanged then the i-th number should coincide with the number from the input data. Otherwise, it is considered that this card was exchanged, and the i-th number should be equal to the number on the card it was exchanged to.

If there are multiple answers, it is allowed to print any of them.


-----Examples-----
Input
6 2
5 6 7 9 4 5

Output
1
5 6 7 9 4 2 

Input
8 6
7 7 7 7 8 8 8 8

Output
6
7 2 4 6 8 1 3 5 

Input
4 1
4 2 1 10

Output
-1

Difficulty: interview

Starter code:

Solutions:
#!/usr/bin/env python3


class CantException(Exception):
    pass


def odd_v(value):
    return 1 if value % 2 == 1 else -1


change_idx = 1

acceptable = {-1: set(), 1: set()}


def change(card_values, oddv, m):
    nonlocal change_idx

    if acceptable[oddv]:
        res = acceptable[oddv].pop()
        card_values.add(res)
        return res

    change_idx_start = change_idx

    while change_idx in card_values or odd_v(change_idx) != oddv:
        if change_idx not in card_values:
            acceptable[odd_v(change_idx)].add(change_idx)
        change_idx += 1
        if change_idx > m:
            change_idx = 1
        if change_idx == change_idx_start:
            raise CantException()

    res = change_idx
    card_values.add(res)

    change_idx += 1
    if change_idx > m:
        change_idx = 1
    return res


def solve():
    n, m = list(map(int, input().split()))
    cards = list(map(int, input().split()))

    odd_balance = 0
    card_values = set()
    indices_to_be_changed = set()

    for i, c in enumerate(cards):
        odd_balance += odd_v(c)
        if c in card_values:
            indices_to_be_changed.add(i)
        card_values.add(c)

    # print("indices to be changed: ", indices_to_be_changed)
    change_count = len(indices_to_be_changed)

    for i in indices_to_be_changed:
        if odd_v(cards[i]) * odd_balance <= 0:
            #print("Changing ", cards[i])
            cards[i] = change(card_values, odd_v(cards[i]), m)
            #print("Changed to ", cards[i])
        else:
            #print("For teh balance changing ", cards[i])
            odd_balance -= 2 * odd_v(cards[i])
            cards[i] = change(card_values, - odd_v(cards[i]), m)
            #print("Changed to ", cards[i])

    #print("current odd balance:", odd_balance)
    for i in range(len(cards)):
        if odd_balance == 0:
            break
        if odd_v(cards[i]) * odd_balance > 0:
            # print("gonna change")
            change_count += 1
            odd_balance -= 2 * odd_v(cards[i])
            cards[i] = change(card_values, -odd_v(cards[i]), m)

    odd_balance = 0
    for i, c in enumerate(cards):
        odd_balance += odd_v(c)
    if odd_balance != 0:
        print(odd_balance)
        print("WTFFFFF")

    return change_count, cards


def __starting_point():
    try:
        change_cnt, cards = solve()
        print(change_cnt)
        print(" ".join(map(str, cards)))
    except CantException:
        print("-1")

__starting_point()

n, m = map(int, input().split())
a = list(map(int, input().split()))

counter = 0

s = set(a)
nech = set()
chet = set()
for elem in a:
    if elem % 2:
        nech.add(elem)
    else:
        chet.add(elem) 

while len(nech) > n // 2:
    nech.pop()
while len(chet) > n // 2:
    chet.pop()

l_n =  set([i for i in range(1, min(m + 1, 1000000), 2)])
l_ch = set([i for i in range(2, min(m + 1, 1000000), 2)])

l_ch.difference_update(chet)
l_n.difference_update(nech)

#print(l_ch)
#print(l_n, nech)

if len(l_ch) + len(chet) < n // 2 or len(l_n) + len(nech) < n // 2:
    print(-1)
else:
    n1 = len(chet)
    n2 = len(nech)
    for i in range(n):
        if a[i] in chet:
            chet.remove(a[i])
        elif a[i] in nech:
            nech.remove(a[i])
        else:
            counter += 1
            if (n//2 - n1) > 0:
                a[i] = l_ch.pop()
                n1 += 1
            else:
                a[i] = l_n.pop()
                n2 += 1 
        
    print(counter)    
    print(*a)

import sys
import math


def main():
    n,m = map(int,sys.stdin.readline().split())
    x = list(map(int,sys.stdin.readline().split()))

    c = []
    nc = []
    d = {}
    for i in range(n):
        xi = x[i]
        if xi in d:
            continue
        d[xi] = True
        if xi%2 == 0:
            c.append((xi,i))
        else:
            nc.append((xi,i))

    a, b = -1,0

    if len(nc) > len(c):
        c,nc = nc,c
        a,b = b,a

    c = sorted(c, key=lambda x: -x[0])
    d = {}
    r = [0]*n
    for i in range(len(nc)):
        xi,j = nc[i]
        r[j] = xi
        d[xi]= True
        
    for i in range(min(n//2,len(c))):
        xi,j = c[i]
        r[j] = xi
        d[xi]= True
    
    j=0    
    ans=0
    for i in range(len(c),n//2):
        b+=2
        while b in d:
            b+=2
        while r[j]!=0:
            j+=1 
        r[j] = b
        ans+=1
    for i in range(len(nc),n//2):
        a+=2
        while a in d:
            a+=2
        while r[j]!=0:
            j+=1 
        r[j] = a
        ans+=1

    if a>m or b>m:
        print(-1)
        return 
    
    print(ans)
    
    print(' '.join(map(str,r)))


main()

def solve(A, n, m):
    uniq = set(A)
    odd = list([x for x in uniq if x%2])
    even = list([x for x in uniq if x%2 == 0])
    if len(odd) > n//2:
        odd.sort()
        odd = odd[-n//2:]
    if len(even) > n//2:
        even.sort()
        even = even[-n//2:]

    odd_needed = n//2 - len(odd)
    changes = n - len(odd) - len(even)
    k = 1 if odd_needed else 2

    D = {x: True for x in odd + even}
    A1 = A[:]
    for i, a in enumerate(A):
        if a in D and D[a]:
            D[a] = False
        else:
            while k in D:
                k += 2
            if k > m:
                return None
            A1[i] = k
            k += 2
            if odd_needed == 1: k = 2
            if odd_needed >= 1: odd_needed -= 1
    
    return A1, changes
    
n, m = list(map(int, input().split()))
A = [int(x) for x in input().split()]
p = solve(A, n, m)
if p is None:
    print(-1)
else:
    print(p[1])
    print(' '.join(map(str, p[0])))