Minimum Changes to Make Staircase Symmetric

You are given a staircase with N steps, where each step has a certain height given by an array H. Your task is to determine the minimum number of step modifications needed so that the staircase becomes symmetric. A staircase is symmetric if for every index i (0-indexed), the condition

\( H[i] = H[N-i-1] \)

holds true.

For example, if the staircase is described by N = 5 and H = [1, 3, 2, 3, 1], it is already symmetric and no changes are needed. However, if instead you have H = [1, 5, 3, 2, 5, 1] for N = 6, you will need to adjust one step to achieve symmetry.

inputFormat

The first line of input contains a single integer N representing the number of steps in the staircase. The second line contains N space-separated integers which denote the heights of the steps.

outputFormat

Output a single integer: the minimum number of changes required to make the staircase symmetric.

## sample

5
1 3 2 3 1

0

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