Problem:
Score : 200 points

Problem Statement

Given are integers a,b,c and d.
If x and y are integers and a \leq x \leq b and c\leq y \leq d hold, what is the maximum possible value of x \times y?

Constraints

-10^9 \leq a \leq b \leq 10^9

-10^9 \leq c \leq d \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

a b c d

Output

Print the answer.

Sample Input 1

1 2 1 1

Sample Output 1

2

If x = 1 and y = 1 then x \times y = 1.
If x = 2 and y = 1 then x \times y = 2.
Therefore, the answer is 2.

Sample Input 2

3 5 -4 -2

Sample Output 2

-6

The answer can be negative.

Sample Input 3

-1000000000 0 -1000000000 0

Sample Output 3

1000000000000000000

Solution in PyPy3 (7.3.0) (judge verdict: Accepted)

# import numpy as np
import sys, math, heapq
from itertools import permutations, combinations
from collections import defaultdict, Counter, deque
from math import factorial, gcd
from bisect import bisect_left, bisect_right

sys.setrecursionlimit(10 ** 7)
MOD = 10 ** 9 + 7
input = lambda: sys.stdin.readline()[:-1]
pl = lambda x: print(*x, sep="\n")

a, b, c, d = map(int, input().split())

res = -float("inf")
for x in [a, b]:
    for y in [c, d]:
        val = x * y
        res = max(res, val)

print(res)