There is a sequence of
n+2 elements a_{0}, a_{1},…, a_{n+1}
(n <= 3000; -1000 <=
a_{i} 1000). It is known that **a**_{i}
= (a_{i–1} + a_{i+1})/2 – c_{i} for each i=1, 2, ..., n. You are given a_{0}, a_{n+1},
c_{1}, ... , c_{n}. Write a program which calculates a_{1}.

The first line is the number of test cases, followed by a blank line.

For each test case, the first line of an input file 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.

Each test case will be separated by a single line.

## The Output

For each test case, the output file should contain a_{1} in the
same format as a_{0} and a_{n+1}.

Print a blank line between the outputs for two consecutive test cases.

## Sample Input

1
1
50.50
25.50
10.15

27.85