w,h,k=map(int,input().split())
s=0
for i in range(k,0,-1):
s+=2*(w-4*(i-1))+2*(h-4*(i-1))-4
print(s)394. Decode String | 902. Numbers At Most N Given Digit Set |
221. Maximal Square | 1200. Minimum Absolute Difference |
1619B - Squares and Cubes | 1619A - Square String |
1629B - GCD Arrays | 1629A - Download More RAM |
1629C - Meximum Array | 1629D - Peculiar Movie Preferences |
1629E - Grid Xor | 1629F1 - Game on Sum (Easy Version) |
2148. Count Elements With Strictly Smaller and Greater Elements | 2149. Rearrange Array Elements by Sign |
2150. Find All Lonely Numbers in the Array | 2151. Maximum Good People Based on Statements |
2144. Minimum Cost of Buying Candies With Discount | Non empty subsets |
1630A - And Matching | 1630B - Range and Partition |
1630C - Paint the Middle | 1630D - Flipping Range |
1328A - Divisibility Problem | 339A - Helpful Maths |
4A - Watermelon | 476A - Dreamoon and Stairs |
1409A - Yet Another Two Integers Problem | 977A - Wrong Subtraction |
263A - Beautiful Matrix | 180C - Letter |