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 Python (3.8.2) (judge verdict: Runtime Error)

def main():
    N, K = map(int, input().split())
    A = list(map(int, input().split()))

    plus = [A[i] for i in range(N) if A[i] >= 0]
    minus = [A[i] for i in range(N) if A[i] < 0]

    ans = 1

    id = 0
    id2 = 0
    P = len(plus)
    M = len(minus)
    plus.sort(reverse=True)

    mod = 10**9 + 7

    if P == 0:
        if K % 2 == 0:
            minus.sort()
            for i in range(K):
                ans *= minus[i]
                ans %= mod
        else:
            minus.sort(reverse=True)
            for i in range(K):
                ans *= minus[i]
                ans %= mod

    elif M == 0:
        for i in range(K):
            ans *= plus[i]
            ans %= mod

    else:

        p = P // 2
        m = M // 2
        if K > (p+m)*2 and (K % 2 == 1 and P % 2 == 0):  # 絶対値が小さい方から貪欲
            A.sort(key=lambda x: abs(x))
            for i in range(K):
                ans *= A[i]
                ans %= mod

        else:  # 絶対値が大きい方から貪欲
            minus.sort()
            pp = [plus[i]*plus[i+1] for i in range(M // 2)]
            mm = [minus[i] * minus[i+1] for i in range(P//2)]

            id = 0
            id2 = 0

            pp.sort(reverse=True)
            mm.sort(reverse=True)
            pp.append(1)
            mm.append(1)
            for i in range((K // 2) - 1):
                if id == p - 1:
                    ans *= mm[id2]
                    id2 += 1
                elif id2 == m:
                    ans *= pp[id]
                    id += 1
                elif pp[id] >= mm[id2]:
                    ans *= pp[id]
                    id += 1
                else:
                    ans *= mm[id2]
                    id2 += 1

                ans %= mod

            if K % 2 == 1:

                if id >= p-1:
                    ans *= mm[id2]
                    ans *= plus[id*2]
                else:
                    ans *= pp[id]
                    id += 1
                    ans *= pp[id*2]
            else:
                if id == p - 1:
                    ans *= mm[id2]
                    id2 += 1
                elif id2 == m:
                    ans *= pp[id]
                    id += 1
                elif pp[id] >= mm[id2]:
                    ans *= pp[id]
                    id += 1
                else:
                    ans *= mm[id2]
                    id2 += 1

    print(ans % mod)


main()