Problem:
Score : 500 points

Problem Statement

Given are N integers A_1,\ldots,A_N.

We will choose exactly K of these elements. Find the maximum possible product of the chosen elements.

Then, print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Constraints

1 \leq K \leq N \leq 2\times 10^5

|A_i| \leq 10^9

Input

Input is given from Standard Input in the following format:

N K
A_1 \ldots A_N

Output

Print the maximum product modulo (10^9+7), using an integer between 0 and 10^9+6 (inclusive).

Sample Input 1

4 2
1 2 -3 -4

Sample Output 1

12

The possible products of the two chosen elements are 2, -3, -4, -6, -8, and 12, so the maximum product is 12.

Sample Input 2

4 3
-1 -2 -3 -4

Sample Output 2

1000000001

The possible products of the three chosen elements are -24, -12, -8, and -6, so the maximum product is -6.

We print this value modulo (10^9+7), that is, 1000000001.

Sample Input 3

2 1
-1 1000000000

Sample Output 3

1000000000

The possible products of the one chosen element are -1 and 1000000000, so the maximum product is 1000000000.

Sample Input 4

10 10
1000000000 100000000 10000000 1000000 100000 10000 1000 100 10 1

Sample Output 4

999983200

Be sure to print the product modulo (10^9+7).

Solution in PyPy3 (7.3.0) (judge verdict: Wrong Answer)

mod = 10**9+7
N,K = map(int,input().split())
A = list(map(int,input().split()))
A.sort(key=lambda x:-abs(x))
p = []
n = []
for i in range(K):
    a = A[i]
    if a>0:
        p.append(a)
    elif a<0:
        n.append(a)

if len(n)%2==0:
    ans = 1
    for a in n:
        ans *= a
        ans %= mod
    for a in p:
        ans *= a
        ans %= mod
else:
    ap = 0
    an = 0
    for i in range(K,N):
        if ap==0 and A[i]>0:
            ap = A[i]
        if an==0 and A[i]<0:
            an = -A[i]
    if len(p)*len(n)>0:
        ap_ = p[-1]
        an_ = -n[-1]
        if ap_*an_==0:
            ans = 0
        else:
            if ap*ap_>an*an_:
                n.pop()
                p.append(ap)
            else:
                p.pop()
                n.append(-an)
            ans = 1
            for a in n:
                ans *= a
                ans %= mod
            for a in p:
                ans *= a
                ans %= mod
    elif len(p)>0:
        ans = 1
        for a in p:
            ans *= a
            ans %= mod
    elif len(n)>0:
        ans = 1
        for a in n:
            ans *= a
            ans %= mod
if len(p)+len(n)<K:
    ans = 0
if len(p)==0 and len(n)==K and K%2==1:
    An = [A[i] for i in range(N) if A[i]<0]
    An.sort()
    An = An[::-1]
    ans = 1
    for i in range(K):
        ans *= An[i]
        ans %= mod
print(ans)