You have a plate and you want to add some gilding to it. The plate is a rectangle that we split into $w\times h$ cells. There should be $k$ gilded rings, the first one should go along the edge of the plate, the second one — $2$ cells away from the edge and so on. Each ring has a width of $1$ cell. Formally, the $i$-th of these rings should consist of all bordering cells on the inner rectangle of size $(w - 4(i - 1))\times(h - 4(i - 1))$.

 [Image] The picture corresponds to the third example. 

Your task is to compute the number of cells to be gilded.


-----Input-----

The only line contains three integers $w$, $h$ and $k$ ($3 \le w, h \le 100$, $1 \le k \le \left\lfloor \frac{min(n, m) + 1}{4}\right\rfloor$, where $\lfloor x \rfloor$ denotes the number $x$ rounded down) — the number of rows, columns and the number of rings, respectively.


-----Output-----

Print a single positive integer — the number of cells to be gilded.


-----Examples-----
Input
3 3 1

Output
8

Input
7 9 1

Output
28

Input
7 9 2

Output
40



-----Note-----

The first example is shown on the picture below.

 [Image] 

The second example is shown on the picture below.

 [Image] 

The third example is shown in the problem description.

Difficulty: interview

Starter code:

Solutions:
w, h, k = map(int, input().split())
ans = 0
for i in range(k):
	ans += w * 2 + (h - 2) * 2
	#print(ans, h, w)
	w -= 4
	h -= 4
print(ans)

w, h, k = list(map(int, input().split()))
p = (w + h) * 2 - 4
res = 0

for i in range(k):
    res += p
    p -= 16
    
print(res)


N, W, k = map(int, input().split())
res = 0
for i in range(k):
    res += (N + W) * 2 - 4
    N -= 4
    W -= 4
print(res)

w, h, k = map(int, input().split())
gold = 0
for i in range(k):
    gold += (w * h) - (w - 2) * (h - 2)
    w -= 4
    h -= 4
print(gold)

w, h, k = map(int, input().split())
ans = 0
for i in range(k):
    ans += w * 2 + (h - 2) * 2
    w -= 4
    h -= 4
print(ans)

import sys
import string
from math import gcd
import getpass
import math
from decimal import Decimal


def ria():
    return [int(i) for i in input().split()]


if getpass.getuser() != 'frohenk':
    filename = 'half'
    # sys.stdin = open('input.txt')
    # sys.stdout = open('output.txt', 'w')
else:
    sys.stdin = open('input.txt')
    # sys.stdin.close()

w, h, k = ria()

suma = 0
for i in range(k):
    suma += w * 2 + h * 2 - 4
    w -= 4
    h -= 4
print(suma)

n, m, k = map(int, input().split())
ans = 0
while (k > 0 and n > 0 and m > 0):
    ans += (n + m - 2) * 2
    n -= 4
    m -= 4
    k -= 1
print(ans)

w, h, k = list(map(int, input().split()))
s = 0
for i in range(k):
    s += 2 * w + 2 * (h - 2)
    w -= 4
    h -= 4
print(s)


w, h, k = map(int, input().split())
s = 0
for i in range(k):
    s += 2 * (w - 4 * i) + 2 * (h - 4 * i) - 4
print(s)

w, h, k = list(map(int, input().split()))
sum_ = 0
for i in range(k):
    sum_ += (w - 4 * i + h - 4 * i) * 2 - 4
print(sum_)


n,m,k=list(map(int,input().split()))
s=0
for i in range(k):
    s+=n*2+(m-2)*2
    n-=4
    m-=4
print(s)


w, h, k = map(int, input().split())
res = 0
for i in range(k):
    res += (w - 4 * i + h - 4 * i) * 2 - 4
print(res)

x,y,k = (int(e) for e in input().split(' '))

r = 0

for i in range(k):
  r += 2*(x+y-2)
  x -= 4
  y -= 4

print(r)

""" 
3 3 1
8
"""


w, h, k = list(map(int, input().split()))
res = 0
for i in range(k):
    res += w * 2 + h * 2 - 4
    w -= 4
    h -= 4
print(res)
    


w = input().split(' ')

n = int(w[0])
m = int(w[1])
k = int(w[2])

sm = 0;

while k>0:
    sm+=2*(n+m-2);
    n-=4;
    m-=4;
    k-=1;

print(sm)


w,h,k=list(map(int,input().split()))
s=0
for i in range(k):
    s+=w*2+(h-2)*2
    w-=4
    h-=4
print(s)


n, m, k = map(int, input().split())
x = n
ans = 0
for i in range(k):
    ans+= 2*x
    x -= 4
x = m
for i in range(k):
    ans+= 2*x
    x -= 4
ans -= k*4

print(ans)

x,y,k = [int (i) for i in input().split()]
o = 0
for i in range (k):
    o+= x*2+(y-2)*2
    y-=4
    x-=4
print (o)


n,m,k = list(map(int, input().split()))
ans = 0;
for i in range(k):
    ans+=n*2+m*2-4
    n-=4
    m-=4
print(ans)


(w, h, k) = list(map(int, input().split()))

ans = 0
i = 0
while i < k:
    ans += 2 * w
    w -= 4
    i += 1

h -= 2
i = 0
while i < k:
    ans += 2 * h
    h -= 4
    i += 1

print(ans)


w,h,k=map(int,input().split())
s=0
for i in range(k):
  s+=2*w+2*h-4
  w=w-4
  h=h-4
print(s)

m, n, k = list(map(int,input().split()))
s = 0
for i in range(k):
    s += 2 * m
    s += 2 * n - 4
    m -= 4
    n -= 4
print(s)


w,h,k=list(map(int,input().split()))
s=0
for i in range(k):
    s+=2*(w-2-4*i)+2*(h-2-4*i)+4
print(s)
    
        


w, h, k = list(map(int, input().split()))
ans = 0
for i in range(k):
    ans += (2 * h + (2 * w) - 4)
    h -= 4
    w -= 4
print(ans)


w, h, k = map(int, input().split())
r = 0
for i in range(k):
    r += w * 2
    r += (h - 2) * 2
    w -= 4
    h -= 4
print(r)