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())
h = int(input())

# (a+b)*h/2
answer = (a + b) * h / 2
print(answer)


a = int(input())
b = int(input())
h = int(input())

# (a+b)*h/2
answer = (a + b) * h / 2
print(int(answer))
