CF1C.Ancient Berland Circus

Nowadays all circuses in Berland have a round arena with diameter 13 meters, but in the past things were different.

In Ancient Berland arenas in circuses were shaped as a regular (equiangular) polygon, the size and the number of angles could vary from one circus to another. In each corner of the arena there was a special pillar, and the rope strung between the pillars marked the arena edges.

Recently the scientists from Berland have discovered the remains of the ancient circus arena. They found only three pillars, the others were destroyed by the time.

You are given the coordinates of these three pillars. Find out what is the smallest area that the arena could have.

如今，贝尔兰（Berland）所有马戏团的表演场均为直径为 13 米的圆形场地，但古代的情况却有所不同。

在古贝尔兰，马戏团的表演场呈正多边形（等角多边形）形状，其尺寸与边数（即顶点数）因马戏团而异。表演场的每个顶点处均设有一根特殊立柱，立柱之间用绳索连接，从而标示出表演场的边界。

近日，贝尔兰的科学家们发现了某座古代马戏团表演场的遗迹，但仅找到三根立柱，其余立柱均已毁于历史长河之中。

现给出这三根立柱的坐标，请计算该表演场可能具有的最小面积。

The input file consists of three lines, each of them contains a pair of numbers –– coordinates of the pillar. Any coordinate doesn't exceed 1000 by absolute value, and is given with at most six digits after decimal point.

输入文件包含三行，每行包含一对数字——即柱子的坐标。任意坐标的绝对值不超过 1000，且小数点后最多有六位数字。

Output the smallest possible area of the ancient arena. This number should be accurate to at least 6 digits after the decimal point. It's guaranteed that the number of angles in the optimal polygon is not larger than 100.

输出古代竞技场的最小可能面积。该数值的小数点后至少保留 6 位有效数字。保证最优多边形的顶点数不超过 100。