a, b, c = 1, 2, "runoob"
print(c)
print(1//2, 1.0/2.0)
a=[2,'a']
print(a*2)
a＝float(input(＂please input a:＂))
b＝float(input(＂please input b:＂))
c＝float(input(＂please input c:＂))
if __________________________:
p=(a+b+c)/2
s=(p*(p-a)*(p-b)*(p-c))**0.5
print("三角形的面积是：",s)
else:
print("构不成三角形")
