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)

N, K = map(int, input().split())
A = list(map(int, input().split()))
mod = 1000000007

zeros = []
pluss = []
minuss = []

for i in range(N):
    if A[i]>0:
        pluss.append(A[i])
    elif A[i]==0:
        zeros.append(A[i])
    else:
        minuss.append(A[i])

pluss = sorted(pluss, reverse = True)
minuss = sorted(minuss)

if len(pluss) + (min(len(minuss), K)//2)*2 >= K:
    answer_type = 1
elif len(zeros) > 0:
    answer_type = 2
else:
    answer_type = 3


#%%
rest = K
if answer_type == 1:
    plus_now = 0
    minus_now = 0
    minus_counter = 0
    answer = 1
    for i in range(K):
        if plus_now < len(pluss):
            plus_target = pluss[plus_now]
        else:
            plus_target = -1000000000000
        
        if minus_now < len(minuss):
            minus_target = -minuss[minus_now]
        else:
            minus_target = -1000000000000
        
        if plus_target >= minus_target:
            answer = (answer*plus_target)%mod
            plus_now += 1
        else:
            answer = (answer*minus_target)%mod
            minus_now += 1
            minus_counter += 1
    
    if minus_counter%2 == 1:
        if minus_now >= len(minuss):
            answer = answer * pow(-minuss[minus_now-1],mod-2,mod)
            answer = answer * pluss[plus_now]
        elif plus_now >= len(pluss):
            answer = answer * pow(pluss[plus_now-1],mod-2,mod)
            answer = answer * -minuss[minus_now]
        elif pluss[plus_now]/(-1*minuss[minus_now-1]) > -1*minuss[minus_now]/(pluss[plus_now-1]):
            answer = answer * pow(-minuss[minus_now-1],mod-2,mod)
            answer = answer * pluss[plus_now]
        else:
            answer = answer * pow(pluss[plus_now-1],mod-2,mod)
            answer = answer * pluss[plus_now]
        print(1)

elif answer_type == 2:
    answer = 0
    print(1)
elif answer_type == 3:
    minuss = sorted(minuss, reverse = True)
    pluss = sorted(pluss, reverse = True)
    plus_now = 0
    minus_now = 0
    answer = 1
    for i in range(K):
        if plus_now < len(pluss):
            plus_target = pluss[plus_now]
        else:
            plus_target = 10000000000000
        
        if minus_now < len(minuss):
            minus_target = minuss[minus_now]
        else:
            minus_target = -1000000000000  
        
        if plus_target <= -minus_target:
            answer = (answer*plus_target)%mod
            plus_now += 1
        else:
            answer = (answer*minus_target)%mod
            minus_now += 1
print(answer%mod)