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,b,h=(int(input()) for _ in range(3))
print(int((a+b)*.5*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(int((a+b)*h/2))

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

print((a+b)*int(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, b, h = (int(input()) for i in [0] * 3)
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())
c = int(input())

print(int((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())
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, b, h = [int(input()) for i in range (3)]
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((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):
print(eval('(%s+%s)*%s//2'%eval('input(),'*3)))

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



def main():
    """Function."""
    a = int(input())
    b = int(input())
    h = int(input())

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


if __name__ == "__main__":
    main()

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

Solution (Python):
from statistics import mean, median,variance,stdev
import sys
import math



a = []
x = int(input())
y = int(input())
z = int(input())


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

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

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(int((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, 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( int((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())

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

Solution (Python):
import sys
import math
import collections
import itertools
import array
import inspect


sys.setrecursionlimit(1000000)



def chkprint(*args):
    names = {
        id(v): k
        for k, v in inspect.currentframe().f_back.f_locals.items()
    }
    print(', '.join(
        names.get(id(arg), '???') + ' = ' + repr(arg) for arg in args))



def to_bin(x):
    return bin(x)[2:]


def li_input():
    return [int(_) for _ in input().split()]


def gcd(n, m):
    if n % m == 0:
        return m
    else:
        return gcd(m, n % m)


def gcd_list(L):
    v = L[0]

    for i in range(1, len(L)):
        v = gcd(v, L[i])

    return v


def lcm(n, m):
    return (n * m) // gcd(n, m)


def lcm_list(L):
    v = L[0]

    for i in range(1, len(L)):
        v = lcm(v, L[i])

    return v



def wfs_d(D, N, K):
    """
    D: 隣接行列(距離付き)
    N: ノード数
    K: 始点ノード
    """

    dfk = [-1] * (N + 1)
    dfk[K] = 0

    cps = [(K, 0)]
    r = [False] * (N + 1)
    r[K] = True
    while len(cps) != 0:
        n_cps = []
        for cp, cd in cps:
            for i, dfcp in enumerate(D[cp]):
                if dfcp != -1 and not r[i]:
                    dfk[i] = cd + dfcp
                    n_cps.append((i, cd + dfcp))
                    r[i] = True

        cps = n_cps[:]

    return dfk



def dfs_d(v, pre, dist):
    """
    v:  現在のノード
    pre: １つ前のノード
    dist: 現在の距離

    以下は別途用意する
    D: 隣接リスト(行列ではない)
    D_dfs_d: dfs_d関数で用いる，始点ノードから見た距離リスト
    """

    global D
    global D_dfs_d

    D_dfs_d[v] = dist

    for next_v, d in D[v]:
        if next_v != pre:
            dfs_d(next_v, v, dist + d)

    return


def sigma(N):
    ans = 0
    for i in range(1, N + 1):
        ans += i
    return ans


def comb(n, r):
    if n - r < r: r = n - r
    if r == 0: return 1
    if r == 1: return n

    numerator = [n - r + k + 1 for k in range(r)]
    denominator = [k + 1 for k in range(r)]

    for p in range(2, r + 1):
        pivot = denominator[p - 1]
        if pivot > 1:
            offset = (n - r) % p
            for k in range(p - 1, r, p):
                numerator[k - offset] /= pivot
                denominator[k] /= pivot

    result = 1
    for k in range(r):
        if numerator[k] > 1:
            result *= int(numerator[k])

    return result

def bisearch(L, target):
    low = 0
    high = len(L) - 1
    
    while low <= high:
        mid = (low + high) // 2
        guess = L[mid]
        if guess == target:
            return True
        elif guess < target:
            low = mid + 1
        elif guess > target:
            high = mid - 1
    if guess != target:
        return False



dp = None


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

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


main()

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

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

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

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

Solution (Python):
head = int(input())
bottom = int(input())
height = int(input())

ans = int(((head + bottom) * height) / 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())
h=int(input())
print((a+b)*h//2)

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

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

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

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

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

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

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

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


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

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

Solution (Python):
roop_num = 3
a,b,h = [int(input()) for i in range(roop_num)]
print(int((a+b)*h*0.5))

Solution (Python):
roop_num = 3
a,b,h = [int(input()) for i in range(roop_num)]
print(int((a+b)*h*0.5))

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):
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):


"""
    1 ≤ a ≤ 100
    1 ≤ b ≤ 100
    1 ≤ h ≤ 100
    入力で与えられる値はすべて整数
    h は偶数
"""

def main():
    """
    台形の面積を出力する関数
    """
    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())
length = int(input())

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

print(area)

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

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

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

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

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

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

Solution (Python):
a, b, h = [int(input()) for i in range(1, 4)]
print((a + b) * h // 2)

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

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

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

Solution (Python):
l = [int(input()) for i in range(1, 4)]
print((l[0] + l[1]) * l[2] // 2)

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

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):

print((int(input()) + int(input())) * int(input()) //2)

Solution (Python):
from collections import defaultdict, Counter
from itertools import product, groupby, count, permutations, combinations
from math import pi, sqrt
from collections import deque
from bisect import bisect, bisect_left, bisect_right
from string import ascii_lowercase
from functools import lru_cache
import sys
sys.setrecursionlimit(10000)
INF = float("inf")
YES, Yes, yes, NO, No, no = "YES", "Yes", "yes", "NO", "No", "no"
dy4, dx4 = [0, 1, 0, -1], [1, 0, -1, 0]
dy8, dx8 = [0, -1, 0, 1, 1, -1, -1, 1], [1, 0, -1, 0, 1, 1, -1, -1]


def inside(y, x, H, W):
    return 0 <= y < H and 0 <= x < W


def ceil(a, b):
    return (a + b - 1) // b


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((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(int(ans))

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

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

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

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

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

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

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 _ in range(3))
print(int((a+b)*c/2))

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

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

if __name__ == '__main__':
    main()

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,b,h=map(int,[input()for i in[0]*3]);print(h*(a+b)//2)

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

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

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

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

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

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

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

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):
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):
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(3)]

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

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

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

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

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

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

Solution (Python):

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

Solution (Python):
a = int(raw_input())
b = int(raw_input())
h = int(raw_input())
print (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((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):
a, b, h = list(map(int, [input() for _ in range(3)]))

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

Solution (Python):
import sys
a,b,h=map(int,sys.stdin)
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())

area = (a+b)*h/2

print(int(area))

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

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

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

Solution (Python):
t=[input() for i in range(3)]
a=int(t[0])
b=int(t[1])
h=int(t[2])

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

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

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

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

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

Solution (Python):
l = [int(input()) for i in range(3)]
print('{}'.format(int((l[0]+l[1])*l[2]/2)))

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

Solution (Python):

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

Solution (Python):

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

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

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

Solution (Python):
i=lambda:int(input());print((i()+i())*i()//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):
t = [int(input()) for i in range(3)]

sum = (t[0]+t[1])* t[2]/2
print(int(sum))

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

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):

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

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

Solution (Python):
N = int(input())
K = int(input())
X = int(input())

print((N+K)*X//2)

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

Solution (Python):





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

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

Solution (Python):
def inpn(): return int(input())
print((inpn()+inpn())*inpn()//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 = int(input())
b = int(input())
h = int(input())

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

Solution (Python):
import math
import sys

def getinputdata():

    
    array_result = []
    
    data = input()

    
    array_result.append(data.split(" "))

    flg = 1

    try:


        while flg:

            data = input()

            array_temp = []

            if(data != ""):
                
                array_result.append(data.split(" "))

                flg = 1

            else:

                flg = 0
    finally:


        return array_result





arr_data = getinputdata()

a = int(arr_data[0][0])
b = int(arr_data[1][0])
h = int(arr_data[2][0])


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

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

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

Solution (Python):
def i1():
 return int(input())
def i2():
 return [int(i) for i in input().split()]
a=i1()
b=i1()
h=i1()
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):

"""
https://beta.atcoder.jp/contests/abc045/tasks/abc045_a

"""
import sys
from sys import stdin
input = stdin.readline


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


def main(args):
    a = int(input())
    b = int(input())
    h = int(input())
    ans = solve(a, b, h)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])

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

    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(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(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())

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