A - Golden Plate CodeForces - 1072A ----小shi shi 给小天天的 Day1

You have a plate and you want to add some gilding to it. The plate is a rectangle that we split into w×hw×h cells. There should be kk gilded rings, the first one should go along the edge of the plate, the second one — 22 cells away from the edge and so on. Each ring has a width of 11 cell. Formally, the ii-th of these rings should consist of all bordering cells on the inner rectangle of size (w−4(i−1))×(h−4(i−1))(w−4(i−1))×(h−4(i−1)).

 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 ww, hh and kk (3≤w,h≤1003≤w,h≤100, 1≤k≤⌊min(n,m)+14⌋1≤k≤⌊min(n,m)+14⌋, where ⌊x⌋⌊x⌋ denotes the number xx 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.

The second example is shown on the picture below.

The third example is shown in the problem description.

题意：

给你一个w*h个小方格组成的长方形 ， 求该长方形涂了金色的方格数。

K层 ， 第一层是长方形的四周 ， 接下来每次都会往内部进俩格。

思路：

就求周长呗 ， k>1 ， 长宽各减二再继续加上周长 ， 直到K次结束。

代码：

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int w , h , k , ans = 0;
	scanf("%d %d %d" , &w , &h , &k);
	while(k--)
	{
		ans+= (w+h-2)*2;
		w = w-4;
		h = h-4;
		
	}
	printf("%d\n" , ans);
	return 0;
 }