import math
import sys


def input():
    return sys.stdin.readline().strip()


def main():

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

    def d(x, y):
        return [(x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)]

    def ccw(p, q, r):
        (x1, y1), (x2, y2), (x3, y3) = p, q, r
        return abs((x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1)) / 2

    ans = 0
    for i in d(x1, y1):
        for j in d(x2, y2):
            for k in d(x3, y3):
                ans = max(ans, ccw(i, j, k))
    print(f"{ans:.1f}")


if __name__ == "__main__":
    main()