You are given a trapezoid. The lengths of its upper base, lower base, and height are a, b, and h, respectively.    An example of a trapezoid  Find the area of this trapezoid.
a = int(input())
b = int(input())
c = int(input())

e = a+b

print(e*c/2)
a = int(input())
b = int(input())
h = int(input())
 
c = a+b
d = h/2
 
e = int(c*d)

print(e)