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

ans = 0
for nx1, ny1 in ((x1 + 1, y1), (x1 - 1, y1), (x1, y1 + 1), (x1, y1 - 1)):
    for nx2, ny2 in ((x2 + 1, y2), (x2 - 1, y2), (x2, y2 + 1), (x2, y2 - 1)):
        for nx3, ny3 in ((x3 + 1, y3), (x3 - 1, y3), (x3, y3 + 1), (x3, y3 - 1)):
            dx1, dy1 = nx2 - nx1, ny2 - ny1
            dx2, dy2 = nx3 - nx1, ny3 - ny1
            ans = max(ans, abs(dx1 * dy2 - dy1 * dx2))
print(f'{ans / 2:.1f}')