import sys
input = sys.stdin.readline
x1, y1, x2, y2, x3, y3 = map(int, input().split())
ans = 0
dir = [(1, 0), (-1, 0), (0, 1), (0, -1)]
for dx1, dy1 in dir:
    nx1 = x1+dx1
    ny1 = y1+dy1
    for dx2, dy2 in dir:
        nx2 = x2+dx2
        ny2 = y2+dy2
        a1 = nx2-nx1
        b1 = ny2-ny1
        for dx3, dy3 in dir:
            nx3 = x3+dx3
            ny3 = y3+dy3
            a2 = nx3-nx1
            b2 = ny3-ny1
            s = abs(a1*b2-a2*b1)/2
            ans = max(ans, s)
print(ans)