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)

from collections import deque

N, K = map(int, input().split())
A = list(map(int, input().split()))
mod = pow(10,9)+7

A.sort(reverse=True)

deque = deque()
for a in A:
    deque.append(a)

ans = 1
cnt = 0
if K%2 == 1:
    ans *= deque.popleft()
    cnt += 1
    
if ans <= 0:
    for i in range(K-1):
        ans *= deque.popleft()
        ans %= mod
else:
    while cnt < K:
        x1 = deque.popleft()
        x2 = deque.popleft()
        if deque:
            y1 = deque.pop()
        else:
            pop = 1
        if deque:
            y2 = deque.pop()
        else:
            pop = -pow(10,9)-1
        if x1*x2 < y1*y2:
            ans *= y1*y2
            ans %= mod
            deque.appendleft(x2)
            deque.appendleft(x1)
            cnt += 2
        else:
            ans *= x1*x2
            ans %= mod
            deque.append(y2)
            deque.append(y1)
            cnt += 2
            
print(ans)