import matha = float(input('依次输入边长：\n'))b = float(input())c = float(input())while a<=0 or b<=0 or c<=0 or a+b<c or a+c<b or b+c<a:print('此三边不构成三角形，请重新输入')a = float(input('依次输入边长：\n'))b = float(input())c = float(input())
p = (a+b+c)/2x = p*(p-a)*(p-b)*(p-c)s = math.sqrt(x)print('面积：' + str(s))