浙大 PTA练习系统数值分析NA1003 三角追赶法的应用-One day, CYLL found an interesting piece of commercial　newspaper: the Cyber-restaurant was offering a kind of　Lunch Special　which was said that one could　buy one get two for free . That is, if you buy one of the dishes on their menu, denoted by d

i

　with price p

i

, you may get the two neighboring dishes d

i− 1

　and d

i+1

　for free! If you pick up d

1

, then you may get d

2

　and the last one d

n

　for free, and if you choose the last one d

n

, you may get d

n− 1

　and d

1

　for free.

However, after investigation CYLL realized that there was no free lunch at all. The price p

i

　of the i-th dish was actually calculated by adding up twice the cost c

i

　of the dish and half of the costs of the two　free　dishes. Now given all the prices on the menu, you are asked to help CYLL find the cost of each of the dishes.