# Frog Jumping

## 题意翻译

###### 题目描述 对于给定的$a,b,k$，初始状态$x=0$，第$i$次操作满足以下规则： - $i$为奇数，$x=x+a$ - $i$为偶数，$x=x-b$ 求$k$次操作后$x$的值 ###### 输入格式 **题目有多组数据** 第一行一个整数$t(1\leq t\leq1000)$表示数据组数 接下来$t$行，每行三个整数$a,b,k(1\leq a,b,k\leq10^9)$表示每组数据 ###### 输出格式 输出共$t$行，第$i$行表示第$i$组数据的答案

## 题目描述

A frog is currently at the point $0$ on a coordinate axis $Ox$ . It jumps by the following algorithm: the first jump is $a$ units to the right, the second jump is $b$ units to the left, the third jump is $a$ units to the right, the fourth jump is $b$ units to the left, and so on. Formally: - if the frog has jumped an even number of times (before the current jump), it jumps from its current position $x$ to position $x+a$ ; - otherwise it jumps from its current position $x$ to position $x-b$ . Your task is to calculate the position of the frog after $k$ jumps. But... One more thing. You are watching $t$ different frogs so you have to answer $t$ independent queries.

## 输入输出格式

### 输入格式

The first line of the input contains one integer $t$ ( $1 \le t \le 1000$ ) — the number of queries. Each of the next $t$ lines contain queries (one query per line). The query is described as three space-separated integers $a, b, k$ ( $1 \le a, b, k \le 10^9$ ) — the lengths of two types of jumps and the number of jumps, respectively.

### 输出格式

Print $t$ integers. The $i$ -th integer should be the answer for the $i$ -th query.

## 输入输出样例

### 输入样例 #1


6
5 2 3
100 1 4
1 10 5
1000000000 1 6
1 1 1000000000
1 1 999999999


### 输出样例 #1


8
198
-17
2999999997
0
1


## 说明

In the first query frog jumps $5$ to the right, $2$ to the left and $5$ to the right so the answer is $5 - 2 + 5 = 8$ . In the second query frog jumps $100$ to the right, $1$ to the left, $100$ to the right and $1$ to the left so the answer is $100 - 1 + 100 - 1 = 198$ . In the third query the answer is $1 - 10 + 1 - 10 + 1 = -17$ . In the fourth query the answer is $10^9 - 1 + 10^9 - 1 + 10^9 - 1 = 2999999997$ . In the fifth query all frog's jumps are neutralized by each other so the answer is $0$ . The sixth query is the same as the fifth but without the last jump so the answer is $1$ .