from sys import stdin
def input(): return stdin.readline()[:-1]


def solve():
    x1, y1, x2, y2, x3, y3 = map(int, input().split())
    coooor = [[x1, y1], [x2, y2], [x3, y3]]
    
    ans = 0
    def dfs(index, coords):
        if index == 3:
            x1, y1 = coords[0]
            x2, y2 = coords[1]
            x3, y3 = coords[2]
            nonlocal ans
            ans = max(ans, abs((x1*(y2-y3) + x2*(y3-y1) + x3*(y1-y2))/2))
            return

        x, y = coooor[index]
        tuple1 = (x + 1, y)
        tuple2 = (x - 1, y)
        tuple3 = (x, y + 1)
        tuple4 = (x, y - 1)
        coords.append(tuple1)
        dfs(index + 1, coords)
        coords.pop()
        coords.append(tuple2)
        dfs(index + 1, coords)
        coords.pop()
        coords.append(tuple3)
        dfs(index + 1, coords)
        coords.pop()
        coords.append(tuple4)
        dfs(index + 1, coords)
        coords.pop()
    
    dfs(0, [])
    print(ans)

solve()