a = int(eval(input()))

b = int(eval(input()))

h = int(eval(input()))



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

b = int(eval(input()))

h = int(eval(input()))

print((((a+b)*h)//2))

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

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

-print(((a + b) * h // 2)) +print((((a + b) * h) // 2))