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

Solution (Python):
a,b,h=map(int,open(0))
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())


A=(a+b)*h/2
print(round(A))

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

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

Solution (Python):
l = []
for _ in range(3):
    l.append(int(input()))

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

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

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())
iarea = ((a + b) *h)  >>  1 
print(iarea)

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

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

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

answer=(a+b)*h*1/2
print(round(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)*h/2))

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

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

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

Solution (Python):
l = [0]*3
for i in range(3):
    l[i] = int(input())

print(int(((l[0] + l[1]) * l[2] / 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(int((a+b)*h/2))

Solution (Python):
a=int(input())
b=int(input())
h=int(input())
print("{}".format((a+b)*h//2))

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

print((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())

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

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

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

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

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

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

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

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

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

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())

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

print(int(rst))

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())

S=(a+b)*h/2

print(int(S))

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

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((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())

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):

def read_input():
    a = int(input())
    b = int(input())
    h = int(input())
    return a, b, h


def submit():
    a, b, h = read_input()
    area = (a + b) * h / 2

    print(int(area))

if __name__ == '__main__':
    submit()

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 >> 1))

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

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

Solution (Python):


def solve(a, b, h):
    print(int((a+b)*h/2))

if __name__ == '__main__':
    a  = int(input())
    b = int(input())
    h = int(input())

    solve(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((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):
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())

if  a >= 1 and a <= 100 \
and b >= 1 and b <= 100 \
and h >= 1 and h <= 100 \
and h % 2 == 0 :
  ans = int((a + b) * h / 2)
  
  print(ans)

Solution (Python):
import functools

import os
import sys

sys.setrecursionlimit(10000)
INF = float('inf')


def inp():
    return int(input())


def inpf():
    return float(input())


def inps():
    return input()


def inl():
    return list(map(int, input().split()))


def inlf():
    return list(map(float, input().split()))


def inls():
    return input().split()


def inpm(line):
    return [inp() for _ in range(line)]


def inpfm(line):
    return [inpf() for _ in range(line)]


def inpsm(line):
    return [inps() for _ in range(line)]


def inlm(line):
    return [inl() for _ in range(line)]


def inlfm(line):
    return [inlf() for _ in range(line)]


def inlsm(line):
    return [inls() for _ in range(line)]


def Yesif(cond):
    print('Yes' if cond else 'No')


def YESIF(cond):
    print('YES' if cond else 'NO')


def yesif(cond):
    print('yes' if cond else 'no')


a, b, c = inpm(3)

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

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

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

Solution (Python):


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

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

Solution (Python):

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

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

Solution (Python):
import sys

def main():
    input = sys.stdin.readline
    a = int(input())
    b = int(input())
    h = int(input())

    return (a+b) * h // 2


if __name__ == '__main__':
    print(main())

Solution (Python):

a, b, h = list(map(int, [input().rstrip() 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((a+b)*h//2)

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

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

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

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

Solution (Python):


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

a, b, h = n

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

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

Solution (Python):
from sys import stdin
input=[]
for i in range(3):
  input.append(stdin.readline().strip())
  
a=int(input[0])
b=int(input[1])
h=int(input[2])
sum=(a+b)*h/2
print(int(sum))

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

Solution (Python):
a, b, h = eval("int(input())," * 3)
print(int((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):
a=int(input())
b=int(input())
h=int(input())
print(int(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(int((a+b)*h/2))

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Solution (Python):
def trapezoids(a: int, b: int, h: int) -> int:
    return (a + b) * h // 2


if __name__ == "__main__":
    a, b, h = [int(input()) for _ in range(3)]
    ans = trapezoids(a, b, h)
    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())

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

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

Solution (Python):


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

x = (a+b)*h/2

print(round(x))

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

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

Solution (Python):
from functools import reduce

def main():
    
    

    
    

    
    
    
    
    

    
    
    
    
    
    
    N = int(input().rstrip())
    K = int(input().rstrip())
    X = int(input().rstrip())
    print(int((N+K)*X/2))   
   
if __name__ == '__main__':
    main()

Solution (Python):
print(int((int(input())+int(input()))*int(input())*0.5))

Solution (Python):
a,b,h = eval('int(input()),'*3)
print(int((a+b)*h*0.5))

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

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

Solution (Python):

from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007


a,b,h = IR(3)
print(((a+b)*h)//2)





"""
h,w,n = LI()
dp = [0 for i in range(10)]
dp[0] = (h-2)*(w-2)
q = defaultdict(int)
for i in range(n):
    a,b = LI()
    a -= 1
    b -= 1
    for i in [-1,0,1]:
        for j in [-1,0,1]:
            if 0 < a+i < h-1 and 0 < b+j < w-1:
                q[(a+i)*w+b+j] += 1
                dp[q[(a+i)*w+b+j]] += 1
                dp[q[(a+i)*w+b+j]-1] -= 1
for i in dp:
    print(i)
"""

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

Solution (Python):

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

if __name__=='__main__':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())
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(h*(a+b)/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(int((a+b)*h/2))

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,b,c=[int(input()) for i in range(3)]
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,b,h = [int(input()) for _ in '111']
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):
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())
print(int((a+b)*h/2))

Solution (Python):
a, b, h = map(int, [input() for x in range(3)])
print((a+b)*h>>1)

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())
ans = (a+ int(input()))/2
print(int(ans * int(input())))

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

res = (a+b)*h/2
print('{0:.0f}'.format(res))

Solution (Python):
from sys import exit

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





exit()

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())

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

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

result = int((1/2) * (a+b) * h)
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,b,h=int(input()),int(input()),int(input())
print((a+b)*h//2)

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

Solution (Python):
list = []
for i in range(3):
    list.append(int(input()))

print(int((list[0]+list[1])*list[2]/2))

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

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

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

Solution (Python):
def main() -> None:
    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())

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

Solution (Python):


a = int(input())

b = int(input())

h = int(input())



print("{:.0f}".format((a+b)*h/2))

Solution (Python):
from itertools import combinations, product


def gcd(a, b):
    if a < b:
        a, b = b, a
    while b != 0:
        a, b = b, a % b
    return a

def lcm(a, b):
    return a * b // gcd(a, b)


def get(fmt):
    ps = input().split()
    r = []
    for p, t in zip(ps, fmt):
        if t == "i":
            r.append(int(p))
        if t == "f":
            r.append(float(p))
        if t == "s":
            r.append(p)
    if len(r) == 1:
        r = r[0]
    return r

def put(*args, **kwargs):
    print(*args, **kwargs)


def rep(n, f, *args, **kwargs):
    return [f(*args, **kwargs) for _ in range(n)]
    
def rep_im(n, v):
    return rep(n, lambda: v)
    
YES_NO = ["NO", "YES"]


a, b, h = rep(3, get, "i")

put((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((b+a)*0.5 * h))

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

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

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

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

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

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

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

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

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

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

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

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

Solution (Python):
a=int(input())
b=int(input())
c=int(input())
s=int((a+b)*c/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):
from sys import stdin
a = int(stdin.readline().rstrip())
b = int(stdin.readline().rstrip())
h = int(stdin.readline().rstrip())
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):
import sys
input = sys.stdin.readline

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

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

Solution (Python):
import sys
stdin = sys.stdin

def li(): return map(int, stdin.readline().split())
def li_(): return map(lambda x: int(x)-1, stdin.readline().split())
def lf(): return map(float, stdin.readline().split())
def ls(): return stdin.readline().split()
def ns(): return stdin.readline().rstrip()
def lc(): return list(ns())
def ni(): return int(stdin.readline())
def nf(): return float(stdin.readline())

a = ni()
b = ni()
h = ni()

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 = 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())
print((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(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):

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

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

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

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

Solution (Python):
a,b,h = map(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)*h//2)

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

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())

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

print(ans)
print()

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

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

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

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

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

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()),int(input()),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):
""" AtCoder """

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

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

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

Solution (Python):

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

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((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 = list(map(int, [input() for x in range(3)]))
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))
print((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, b, h = [int(input()) for _ in range(3)]
print(int(((a+b)*h)/2))

Solution (Python):
print(int((int(input())+int(input()))*int(input())*1/2))

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

print(e)

Solution (Python):
def execute(a, b, h):
    return (a + b) * h // 2


if __name__ == '__main__':
    a = int(input())
    b = int(input())
    h = int(input())
    print(execute(a, b, h))

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

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

area=(a+b)*h >>1

print(area)