Statement

Given n (n is even number and n <= 168) and a permutation of n. Our task is to do the least swap operator so that the value of

the permutation is maximum.

The value of a permutation is

Input

4

1 2 3 4

Output

3

Explain

1 2 3 4

Swap (p[1], p[3]) : 3 2 1 4

Swap (p[3], p[4]) : 3 2 4 1

Swap (p[2], p[4]) : 3 1 4 2

The value of the permutation now is abs(1 — 3) + abs(4 — 1) + abs(2 — 4) = 4

And we do 3 swap operators so the output is 3.