Your are given a sequence of integers a_{1}, …, a_{n}. Find an arithmetic
progression b_{1}, …, b_{n} for which the
value ∑(a_{i} − b_{i})^{2} is minimal. The elements of the progression can be
nonintegral.
Input
The first line contains the number n of elements in the sequence (2 ≤ n
≤ 10^{4}). In the second line you are given the integers a_{1}, …, a_{n};
their absolute values do not exceed 10^{4}.
Output
Output two numbers separated with a space: the first term of the required
arithmetic progression and its difference, with an absolute or relative error
of at most 10^{−6}. It is guaranteed that the answer is unique for all input
data.
Samples
input  output 

4
0 6 10 15
 0.400 4.900

4
2 2 2 2
 2 0

Problem Author: Alex Samsonov
Problem Source: XII USU Open Personal Contest (March 19, 2011)