813. Count Arrangements of N Bishops on M×M Board

Given an integer m (board size), return the maximum number of non-attacking bishops that can be placed on an m×m chessboard. Bishops attack diagonally. The answer is max(0, 2*m - 2) for m >= 2, 1 for m=1, 0 for m<=0.

Input: A single integer m.

Output: Integer.

Examples

Input: 4
Output: 6
Explanation: 2*4-2=6 bishops.

Input: 1
Output: 1
Explanation: One bishop on 1×1.

Input: 0
Output: 0
Explanation: No board.

Constraints

• 0 <= m <= 500

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