print(1//2, 1.0/2.0)
a, b, c = 1, 2, "runoob"
print(c)
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")