import numpy as np
a, b, c, d = map(int, input().split())
hoge = []
hoge.append(a * c)
hoge.append(a * d)
hoge.append(b * c)
hoge.append(b * d)
print(max(hoge))

0b857f4fc459de20142e48e8a52b6dc760b0c56a
<mask token>

<mask token>
hoge.append(a * c)
hoge.append(a * d)
hoge.append(b * c)
hoge.append(b * d)
print(max(hoge))

<mask token>
a, b, c, d = map(int, input().split())
hoge = []
hoge.append(a * c)
hoge.append(a * d)
hoge.append(b * c)
hoge.append(b * d)
print(max(hoge))

import numpy as np
a, b, c, d = map(int, input().split())
hoge = []
hoge.append(a * c)
hoge.append(a * d)
hoge.append(b * c)
hoge.append(b * d)
print(max(hoge))
