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, *A = map(int, open(0).read().split())
MOD = 10 ** 9 + 7

if sum(v == 0 for v in A) > N - K:
    print(0)
    exit()


if all(v <= 0 for v in A):
    if K % 2 == 1 and any(v == 0 for v in A):
        print(0)
        exit()
    x = sorted([v for v in A if v < 0])
    ans = 1
    if K % 2 == 0:
        for i in range(K):
            ans = ans * x[i] % MOD
    else:
        n = len(x)
        for i in range(n - K, n):
            ans = ans * x[i] % MOD

    print(ans)
    exit()


x = sorted([(abs(v), v // abs(v)) for v in A if v != 0])
plus = []
minus = []
for i in range(K):
    v, s = x.pop()
    if s == 1:
        plus.append(v)
    else:
        minus.append(v)


if len(minus) % 2 != 0:
    p_cand = MOD
    m_cand = MOD
    while x:
        v, s = x.pop()
        if s == 1 and p_cand == MOD:
            p_cand = v
        elif s == -1 and m_cand == MOD:
            m_cand = v

    if p_cand == MOD and m_cand != MOD and plus:
        plus.pop()
        minus.append(m_cand)
    elif m_cand == MOD and p_cand != MOD and minus:
        minus.pop()
        plus.append(p_cand)
    elif p_cand != MOD and m_cand != MOD and plus and minus:
        p_org = plus.pop()
        m_org = minus.pop()
        if p_org * p_cand > m_org * m_cand:
            plus.append(p_org)
            plus.append(p_cand)
        else:
            minus.append(m_org)
            minus.append(m_cand)


ans = 1
for v in plus:
    ans = ans * v % MOD
for v in minus:
    ans = ans * (-v) % MOD
print(ans)