X1, Y1, X2, Y2, X3, Y3 = map(int, input().split())
ans = 0
for x1, y1 in [(X1 - 1, Y1), (X1 + 1, Y1), (X1, Y1 - 1), (X1, Y1 + 1)]:
    for x2, y2 in [(X2 - 1, Y2), (X2 + 1, Y2), (X2, Y2 - 1), (X2, Y2 + 1)]:
            for x3, y3 in [(X3 - 1, Y3), (X3 + 1, Y3), (X3, Y3 - 1), (X3, Y3 + 1)]:
                ans = max(ans, abs((x3 - x1) * (y2 - y1) - (x2 - x1) * (y3 - y1)) / 2)
print(ans)