CF40B.Repaintings

A chessboard n × m in size is given. During the zero minute we repaint all the black squares to the 0 color. During the i-th minute we repaint to the i color the initially black squares that have exactly four corner-adjacent squares painted i - 1 (all such squares are repainted simultaneously). This process continues ad infinitum. You have to figure out how many squares we repainted exactly x times.

The upper left square of the board has to be assumed to be always black. Two squares are called corner-adjacent, if they have exactly one common point.

给定一个 $n \times m$ 的棋盘。在第 $0$ 分钟，我们将所有初始为黑色的方格重绘为颜色 $0$。在第 $i$ 分钟，我们将所有初始为黑色且其四个对角相邻方格均被绘制为颜色 $i-1$ 的方格重绘为颜色 $i$（所有满足条件的方格同时重绘）。该过程无限进行下去。你需要计算恰好被重绘了 $x$ 次的方格数量。

棋盘左上角的方格始终视为黑色。若两个方格恰好有一个公共顶点，则称它们为对角相邻。

The first line contains integers n and m (1 ≤ n, m ≤ 5000). The second line contains integer x (1 ≤ x ≤ 109).

第一行包含整数 $n$ 和 $m$（$1 \le n, m \le 5000$）。第二行包含整数 $x$（$1 \le x \le 10^9$）。

Print how many squares will be painted exactly x times.

输出恰好被涂色 x 次的正方形的数量。