clear
input "请输入a：" to a
input "请输入b：" to b
input "请输入c：" to c
if a+b>c and a+c>b and b+c>a
l=(a+b+c)/2
s=sqrt(l*(l-a)(l-b)(l-c))
"其面积为：",s
else
"不能构成三角形"
endif