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

if(a>= 0 and c>= 0):
    print(b*d)
elif(b<=0 and d<=0):
    print(a*c)
elif(a>=0 and d<=0):
    print(a*d)
elif(b<=0 and c>=0):
    print(b*c)
elif(a*c >= b*d):
    print(a*c)
elif(a*c < b*d):
    print(b*d)






7f1bbe0366f73e1d5b20766ade978014e2d2fb65
<mask token>

<mask token>
if a >= 0 and c >= 0:
    print(b * d)
elif b <= 0 and d <= 0:
    print(a * c)
elif a >= 0 and d <= 0:
    print(a * d)
elif b <= 0 and c >= 0:
    print(b * c)
elif a * c >= b * d:
    print(a * c)
elif a * c < b * d:
    print(b * d)

a, b, c, d = map(int, input().split())
if a >= 0 and c >= 0:
    print(b * d)
elif b <= 0 and d <= 0:
    print(a * c)
elif a >= 0 and d <= 0:
    print(a * d)
elif b <= 0 and c >= 0:
    print(b * c)
elif a * c >= b * d:
    print(a * c)
elif a * c < b * d:
    print(b * d)

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

if(a>= 0 and c>= 0):
    print(b*d)
elif(b<=0 and d<=0):
    print(a*c)
elif(a>=0 and d<=0):
    print(a*d)
elif(b<=0 and c>=0):
    print(b*c)
elif(a*c >= b*d):
    print(a*c)
elif(a*c < b*d):
    print(b*d)





