import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

x1, y1, x2, y2, x3, y3 = na()
ans = 0

for a1, a2 in [(x1-1, y1), (x1, y1-1), (x1+1, y1), (x1, y1+1)]:
    for b1, b2 in [(x2-1, y2), (x2, y2-1), (x2+1, y2), (x2, y2+1)]:
        for c1, c2 in [(x3-1, y3), (x3, y3-1), (x3+1, y3), (x3, y3+1)]:
            ans = max(ans, abs((a1-b1)*(c2-b2)-(a2-b2)*(c1-b1)))
print(ans/2)