CF1077A Frog Jumping

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

**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

输出共$t$行，第$i$行表示第$i$组数据的答案

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 $ .