说明：  编写一个三角形类，能根据3个实数构造三角形对象，如果三个实数不满足三角形的条件，则自动构造以最小值为边的等边三角形。输入任意三个数，求构造的三角形面积
(prepared a triangle category, according to three real tectonic triangular object, If the real number is not met three conditions triangle will automatically constructed to the minimum side of an equilateral triangle. 3 importation arbitrary number for the triangular area of tectonic)