a = int(eval(input()))

b = int(eval(input()))

h = int(eval(input()))

print((int((a+b)*h/2)))
a = int(eval(input()))

b = int(eval(input()))

h = int(eval(input()))

s = int((a + b)*h/2)

print(s)

a = int(eval(input()))
b = int(eval(input()))
h = int(eval(input()))
print((int((a + b) * h / 2)))

a = int(eval(input()))
b = int(eval(input()))
h = int(eval(input()))
s = int((a + b) * h / 2)
print(s)

-print((int((a + b) * h / 2))) +s = int((a + b) * h / 2) +print(s)