There is a sequence of N + 2 elements a_{0}, a_{1}, …,
a_{N+1} (1 ≤ N ≤ 3000,
−2000 ≤ a_{i} ≤ 2000). It is known that
a_{i} = (a_{i−1} + a_{i+1})/2 − c_{i}
You are given a_{0}, a_{N+1}, c_{1}, …, c_{N}. Write a program which calculates a_{1}.
Input
The first line contains an integer N. The next two lines consist of numbers a_{0} and a_{N+1} each having two digits after decimal point, and the next N lines contain numbers c_{i} (also with two digits after decimal point), one number per line.
Output
Output a_{1} in the same format as a_{0} and a_{N+1}.
Sample
input  output 

1
50.50
25.50
10.15
 27.85

Problem Author: Dmitry Filimonenkov
Problem Source: Ural State University collegiate programming contest (25.03.2000)