Background

Special for beginners, =)

Description

Given three integers n and x and a,n是小拉猫每天吃的猫粮克数,x是臭二朵每天吃的克数,问a天后它们共吃了多少猫粮*?

*:它们每隔5天发一次情,饭量是之前的½.

Input

Three integers n and x and a, satisfying $0\leq n,x,a\leq 32767$ .

Samples

60 50 6

605

Limitation

1s, 1024KiB for each test case.