Problem:
 Score : 100 points    Problem Statement 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.      Constraints  1≦a≦100  1≦b≦100  1≦h≦100  All input values are integers.  h is even.         Input The input is given from Standard Input in the following format:  a  b  h       Output Print the area of the given trapezoid. It is guaranteed that the area is an integer.        Sample Input 1 3
4
2      Sample Output 1 7  When the lengths of the upper base, lower base, and height are 3 , 4 , and 2 , respectively, the area of the trapezoid is (3+4)×2/2 = 7 .       Sample Input 2 4
4
4      Sample Output 2 16  In this case, a parallelogram is given, which is also a trapezoid.

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
val = [int(input()) for i in range(3)]
print(int((val[0] + val[1]) * val[2] / 2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
def iroha():
    a, b, c = [int(input()) for i in range(3)]
    num = (a+b)*c / 2
    result = int(num)
    print(result)


if __name__ == "__main__":
    iroha()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int(0.5 * h * (a + b)))

Solution (Python):
a,b,h = [int(input()) for _ in range(3)]
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
c=int(input())
print((a+b)*c//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
"""
ABC045 A A - 台形
https://atcoder.jp/contests/abc045/tasks/abc045_a
"""

n = [int(input()) for i in range(3)]

print((n[0]+n[1])*n[2]//2)

Solution (Python):
a, b, h = int(input()), int(input()), int(input())
print((a+b)*h//2)

Solution (Python):
import math
from datetime import date

def main():
	
	a = int(input())
	b = int(input())
	h = int(input())

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

main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b)*h/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
s = (a + b) * h // 2
print(s)

Solution (Python):

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
A, B, H = [int(input()) for _ in range(3)]
print((A+B)*H//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
ans = ((a+b)*h)//2
print(ans)

Solution (Python):
a,b,h = [int(input()) for i in range(3)]
print(int((a+b)*(h/2)))

Solution (Python):
a,b,h = [int(input()) for i in range(3)]
print(int((a+b)/2*h))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
S = (a+b)*h/2
print(round(S))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
ans=max(a,b)*h-(abs(b-a)*h//2)
print(ans)

Solution (Python):
def solve(a, b, h):
    ans = (a+b)*h//2
    return ans


if __name__ == "__main__":
    a = int(input())
    b = int(input())
    h = int(input())
    print(solve(a, b, h))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b) * h // 2)

Solution (Python):
import math
a = int(input())
b = int(input())
h = int(input())

answer = (a + b) * h / 2

print(math.ceil(answer))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b) * h / 2))

Solution (Python):
a = int(input())
b  =int(input())
h = int(input())
 
print(int(((a+b)*h)/2))

Solution (Python):
a = int(input())
b = int(input())
c = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
c = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int(((a+b)*h)/2))

Solution (Python):
a = int(input())
b = int(input())
c = int(input())
print(int((a + b) / 2 * c))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a = []
for i in range (3):
  b = int(input())
  a.append(b)
print(int((a[0]+a[1])*a[2]/2))

Solution (Python):
a = int(input())
b = int(input())
c = int(input())
print(int((a+b)*(c//2)))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

print(answer)

Solution (Python):
def solve():
    a = int(input())
    b = int(input())
    h = int(input())
    print((a + b) * h // 2)


if __name__ == "__main__":
    solve()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a,b,h=[int(input()) for i in range(0,3)]
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
s = (a+b)*h/2
print(int(s))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(round((a+b)*h/2))

Solution (Python):
a = int(input()) 
b = int(input()) 
h = int(input())
print(int((a + b) * h / 2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):














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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
def main():
    a, b, h = int(input()), int(input()), int(input())

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


if __name__ == "__main__":
    main()

Solution (Python):
a,b,h=int(input()),int(input()),int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
from sys import stdin
input = stdin.readline

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

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
z =int((a + b)*h/2)
print(z)

Solution (Python):
a,b,h=[int(input()) for i in range(3)]

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

Solution (Python):
a,b,c=[int(input()) for i in range(3)]
print(int(a+b)*c//2)

Solution (Python):
import sys
def input(): return sys.stdin.readline().strip()

def main():
    a = int(input())
    b = int(input())
    h = int(input())
    print((a + b) * h // 2)




if __name__ == "__main__":
    main()

Solution (Python):

a=int(input())
b=int(input())
h=int(input())
if h%2==0:
    print(int((a+b)*h/2))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):

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

if (1 <= a & a <= 100) & (1 <= b & b <= 100) & (1 <= h & h <= 100):
    if (h % 2 == 0):
        s = int((a + b) * h / 2)
        print(s)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):

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

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

Solution (Python):
a,b,h=[int(input()) for _ in range(3)];print((a+b)*h//2)

Solution (Python):
a = int(input())    
b = int(input())    
h = int(input())    

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

Solution (Python):
import sys
a, b, h =map(int, sys.stdin.readlines())
print((a+b)*h//2)

Solution (Python):




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


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

Solution (Python):
a, b, h = [int(input()) for i in range(3)]

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

Solution (Python):
a = [int(input()) for i in range(3)]
print(int((a[0]+a[1])*a[2]/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

print(int((a+b)*h*0.5))

Solution (Python):
a,b,h = [int(input()) for _ in range(3)]
print(round(((a + b)*h)/2))

Solution (Python):
print(int((int(input())+int(input()))*int(input())/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
s = (a + b) * h / 2
print(int(s))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):


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

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())


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

Solution (Python):
a,b,c=[int(input()) for i in range(3)]
print((a+b)*c//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b) * h / 2))

Solution (Python):

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


area = (a + b) * h // 2


print(area)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
area = (a + b) * h // 2
print(area)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):











input_a = int(input())
input_b = int(input())
input_h = int(input())


result = int((input_a + input_b) * input_h / 2)
print(result)

Solution (Python):
print(eval('(i+i)*i//2'.replace('i','int(input())')))

Solution (Python):
f=lambda:int(input());print((f()+f())*f()//2)

Solution (Python):
a,b,c,d=eval('['+'int(input()),'*3+'0]');print((a+b)*c//2)

Solution (Python):

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


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

Solution (Python):
print((int(input())+int(input()))*int(input())//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):



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

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):





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

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

Solution (Python):

a, b, h = [int(input())for i in range(3)]




S = (a + b) * h // 2




print(S)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):

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



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

Solution (Python):
S_list = [int(input()) for i in range(3)]

result = int((S_list[0] + S_list[1]) * S_list[2] / 2)
print(result)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())


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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(raw_input())
b = int(raw_input())
h = int(raw_input())
s = max(a,b) * h
s-= (max(a,b) - min(a,b))/2.0*h
print int(s)

Solution (Python):

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


answer = (a + b) * h /2


print(int(answer))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):


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

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

print(area)

Solution (Python):




top = int(input())      
bottom = int(input())   
height = int(input())   


area = int((top + bottom) * height / 2)


print(area)

Solution (Python):
sup = int(input())
sub = int(input())
hei = int(input())

print((sup+sub)*hei//2)

Solution (Python):


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

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

print(answer)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a, b, h = (int(input()) for i in range(3))
print(int((a + b) * h / 2))

Solution (Python):
a, b, h = (int(input()) for i in range(3))

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
def main():
    a = int(input())
    b = int(input())
    h = int(input())

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

if __name__ == '__main__':
    main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b) / 2 * h))

Solution (Python):
a, b, h = (int(input()) for i in range(3))
print(int((a + b) / 2 * h))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
c=int(input())
print(int((a+b)*c/2))

Solution (Python):

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


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

print(area)

Solution (Python):
a=int(input())
b=int(input())
c=int(input())
print(int((a+b)*c/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
x=int(input())
y=int(input())
z=int(input())
print((x+y)*z//2)

Solution (Python):







a = int(input())

b = int(input())

h = int(input())



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


print(answer)

Solution (Python):
list1 = []
for i in range(3):
    list1.append(int(input()))
print(int((list1[0] + list1[1]) * list1[2]/2))

Solution (Python):

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

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a,b,h = (int(input()) for T in range(0,3))
print((h*(a+b))//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
 
c=(a+b)*h/2
print(int(c))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):



upper_floor = int(input())
bottom_floor = int(input())
height = int(input())

trapezoid = (upper_floor + bottom_floor) * height / 2
print(int(trapezoid))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a,b,h=map(int,open(0).read().split())
print((a+b)*h//2)

Solution (Python):

def main():
	a = int(input())
	b= int(input())
	h = int(input())
	t = abs(a-b)
	ar = (a+b)*h
	print(ar//2)
if __name__=="__main__":
	main()

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a, b, h=[int(input()) for i in range(3)]
print(int((a+b)*h/2))

Solution (Python):
a, b, h = [int(input()) for _ in range(3)]
print(int((a + b) * h / 2))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
c = int(input())
print( (a+b) * c // 2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
import bisect,collections,copy,heapq,itertools,math,string
import sys
def S(): return sys.stdin.readline().rstrip()
def M(): return map(int,sys.stdin.readline().rstrip().split())
def I(): return int(sys.stdin.readline().rstrip())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LS(): return list(sys.stdin.readline().rstrip().split())
a = I()
b = I()
h = I()
print((a+b)*h//2)

Solution (Python):
a =  int(input())
b =  int(input())
c =  int(input())
print(int((a+b) * c / 2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())


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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a + b) * h) // 2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a, b, h = int(input()), int(input()), int(input())
res = int((a+b)/2 * h)
print(res)

Solution (Python):
u=int(input())
d=int(input())
h=int(input())
print(int((u+d)*h/2))

Solution (Python):

def main():
    a = int(input())
    b = int(input())
    h = int(input())

    print(int((a+b)*h/2))
    
            
if __name__ ==  "__main__":
    main()

Solution (Python):
import sys

read = sys.stdin.read
readline = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 8)
INF = float('inf')
MOD = 10 ** 9 + 7


def main():
    a = int(readline())
    b = int(readline())
    h = int(readline())
    print((a+b)*h//2)


if __name__ == '__main__':
    main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b) * h / 2))

Solution (Python):
A = [int(input()) for i in range(3)]
print((A[0] + A[1]) * A[2] //2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a, b, h = [int(input()) for _ in range(3)]
print((a + b) * h // 2)

Solution (Python):
import math
a = int(input())
b = int(input())
h = int(input())

S = math.floor((a + b) * h / 2)
print(S)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int(((a+b)*h)/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

ans = (a+b)*h / 2

print(int(ans))

Solution (Python):

def main():
    a = int(input())
    b = int(input())
    h = int(input())
    print((a + b) * h // 2)


if __name__ == "__main__":
    main()

Solution (Python):
a=int(input())
b=int(input())
h=int(input())//2
print((a+b)*h)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print( (a+b)*h//2 )

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
import sys
def main():
    read = sys.stdin.read
    a, b, h = map(int, read().split())
    print((a + b) * h // 2)

if __name__ == '__main__':
    main()

Solution (Python):
list = []

for i in range(3):
    list.append(int(input()))

area = (list[0]+list[1])*list[2]/2


print(int(area))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
a,b,h=[int(input()) for i in range(3)]
print((a+b)*h//2)

Solution (Python):







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

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

Solution (Python):
a,b,h = [int(input()) for i in range(3)]
print(int((a + b) * h /2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = [int(input()) for i in range(3)]
print(int((a[0] + a[1]) * a[2] / 2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
area = 0.5*(a+b)*h
print(int(area))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a+b)*h* 0.5))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a+b)*0.5*h))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int((a + b) * h / 2))

Solution (Python):
import sys
import math
import itertools
import bisect
from copy import copy
from collections import deque,Counter
from decimal import Decimal
def s(): return input()
def i(): return int(input())
def S(): return input().split()
def I(): return map(int,input().split())
def L(): return list(input().split())
def l(): return list(map(int,input().split()))
def lcm(a,b): return a*b//math.gcd(a,b)
sys.setrecursionlimit(10 ** 9)
INF = 10**9
mod = 10**9+7

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SI(): return sys.stdin.readline()[:-1]

print((II()+II())*II()//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * (h // 2))

Solution (Python):
a,b,h=int(input()),int(input()),int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
c=int(input())
area=(a+b)*c//2
print(area)

Solution (Python):
from sys  import stdin,stdout

import bisect

import math

def st():
    return list(stdin.readline().strip())

def inp():
    return int(stdin.readline())

def li():
    return list(map(int,stdin.readline().split()))

def mp():
    return map(int,stdin.readline().split())

def pr(n):
    stdout.write(str(n)+"\n")

def soe(limit):
    l=[1]*(limit+1)
    prime=[]
    for i in range(2,limit+1):
        if l[i]:
            for j in range(i*i,limit+1,i):
                l[j]=0

    for i in range(2,limit+1):
        if l[i]:
            prime.append(i)
    return prime

def segsoe(low,high):
    limit=int(high**0.5)+1
    prime=soe(limit)
    n=high-low+1
    l=[0]*(n+1)
    for i in range(len(prime)):
        lowlimit=(low//prime[i])*prime[i]
        if lowlimit<low:
            lowlimit+=prime[i]
        if lowlimit==prime[i]:
            lowlimit+=prime[i]
        for j in range(lowlimit,high+1,prime[i]):
            l[j-low]=1
    for i in range(low,high+1):
        if not l[i-low]:
            if i!=1:
                print(i)
                
def gcd(a,b):
    while b:
        a=a%b
        b,a=a,b
    return a

def power(a,n):
    r=1
    while n:
        if n&1:
            r=(r*a)
        a*=a
        n=n>>1
    return r
    
def solve():
    a=inp()
    b=inp()
    c=inp()
    print(((a+b)*c)//2)



for _ in range(1):
    solve()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
inp=[int(input()) for i in range(3)]
print(int((inp[0]+inp[1])*inp[2]/2))

Solution (Python):
import sys
def I(): return int(sys.stdin.readline().rstrip())

a,b,h = I(),I(),I()
print((a+b)*h//2)

Solution (Python):
a,b,h=(int(input()) for i in range(3))
print(int((a+b)*h/2))

Solution (Python):
def main():
    a = int(input())
    b = int(input())
    h = int(input())
    print(int((a + b) * h / 2))

if __name__ == "__main__":
  main()

Solution (Python):
a=int(input());b=int(input());h=int(input());print(int((a+b)*h/2))

Solution (Python):
def main():
    a = int(input())
    b = int(input())
    h = int(input())
    ans = (a+b)*h//2
    print(ans)


if __name__ == "__main__":
    main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a, b, h= (int(input()) for _ in range(3))
print((a+b)*h // 2)

Solution (Python):

import sys
input = sys.stdin.readline
a = int(input())
b = int(input())
h = int(input())
print(int((a+b)*(h/2)))

Solution (Python):
a = int(input())
b =int(input())
h = int(input())

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

Solution (Python):


def main():

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

    ans = (a + b) * h / 2

    print(int(ans))


if __name__ == "__main__":
    main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(int(0.5*h*(a+b)))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a = [int(input()) for _ in range(3)]

print((a[0]+a[1])*a[2]//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print( (a+b)*h//2 )

Solution (Python):
import sys
a,b,h=map(int,sys.stdin.read().split())
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
c=int((a+b)*h/2)
print(c)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b) * h // 2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
 
print(int(a+b)*h//2 )

Solution (Python):
import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
sys.setrecursionlimit(10 ** 9)
INF = 1 << 60
MOD = 1000000007


def main():
    a, b, h = map(int, read().split())

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

    return


if __name__ == '__main__':
    main()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
a, b, h = (int(input()) for _ in range(3))
print((a + b) * h // 2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
def resolve():
    a = int(input())
    b = int(input())
    h = int(input())
    print(int((a+b)*h/2))

resolve()

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print( ((a + b) * h)//2 )

Solution (Python):
a = [int(input()) for _ in range(3)]
print((a[0]+a[1])*a[2]//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
import sys, os, math, bisect, itertools, collections, heapq, queue

from decimal import Decimal
from collections import defaultdict, deque

sys.setrecursionlimit(10000000)

ii = lambda: int(sys.stdin.buffer.readline().rstrip())
il = lambda: list(map(int, sys.stdin.buffer.readline().split()))
fl = lambda: list(map(float, sys.stdin.buffer.readline().split()))
iln = lambda n: [int(sys.stdin.buffer.readline().rstrip()) for _ in range(n)]

iss = lambda: sys.stdin.buffer.readline().decode().rstrip()
sl = lambda: list(map(str, sys.stdin.buffer.readline().decode().split()))
isn = lambda n: [sys.stdin.buffer.readline().decode().rstrip() for _ in range(n)]

lcm = lambda x, y: (x * y) // math.gcd(x, y)

MOD = 10 ** 9 + 7
MAX = float('inf')


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    a, b, h = ii(), ii(), ii()
    print(((a + b) * h) // 2)


if __name__ == '__main__':
    main()

Solution (Python):
a = int(input())
b = int(input())
h= int(input())
c = (a+b)
res = int(c*h/2)
print(res)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
l=[int(input()) for i in range(3)]

print((l[0]+l[1])*l[2]//2)

Solution (Python):
import sys
import itertools

import time
import math
import heapq
from collections import defaultdict
sys.setrecursionlimit(10 ** 7)
 
INF = 10 ** 18
MOD = 10 ** 9 + 7
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines



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

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h*1/2))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())

res = (a+b)*h//2

print(res)

Solution (Python):
a = input()
b = input()
h = input()
answer = ((int(a) + int(b)) * int(h)) / 2
print(int(answer))

Solution (Python):
a,b,h=[int(input()) for _ in range(3)]
print((a+b)*h//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a = int (input ())
b = int (input ())
h = int (input ())
print ((a+b)*(round(h/2)))

Solution (Python):
import sys

def main(a,b,h):
    return (a+b)*h//2

a =int(sys.stdin.readline().strip())
b =int(sys.stdin.readline().strip())
h =int(sys.stdin.readline().strip())

print(main(a,b,h))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a+b)*h//2)

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print(int((a+b)*h/2))

Solution (Python):
i,p=int,input;print((i(p())+i(p()))*i(p())//2)

Solution (Python):
print(int((int(input())+int(input()))/2*int(input())))

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print(((a+b)*h)//2)

Solution (Python):
a = int(input())
b = int(input())
h = int(input())
print((a + b) * h // 2)

Solution (Python):
A = int(input())
B = int(input())
H = int(input())

print( int(((A+B)*H)/2) )

Solution (Python):
print((int(input())+int(input()))*int(input())//2)

Solution (Python):
print((int(input())+int(input()))*int(input())//2)