import sys
input = sys.stdin.readline

x1,y1,x2,y2,x3,y3=map(int,input().split())

def calc(x1,y1,x2,y2,x3,y3):
    x2-=x1
    x3-=x1
    y2-=y1
    y3-=y1

    return abs(x2*y3-x3*y2)

ANS=0
for x,y in [(x1+1,y1),(x1-1,y1),(x1,y1+1),(x1,y1-1)]:
    for z,w in [(x2+1,y2),(x2-1,y2),(x2,y2+1),(x2,y2-1)]:
        for p,q in [(x3+1,y3),(x3-1,y3),(x3,y3+1),(x3,y3-1)]:
            ANS=max(ANS,calc(x,y,z,w,p,q))

print(ANS/2)