You have an N \times N standard chessboard with alternating black and white squares. You want to place a "frame" of size K \times K (the outer boundary of a K \times K square) on the board.
Count how many positions exist to place the frame such that the number of black squares covered by the frame is exactly equal to the number of white squares covered by the frame.
Input
Two integers N and K (2 \le K \le N \le 10^{9}).
Output
Print the total number of valid positions to place the frame.
Examples
| standard input | standard output |
|---|
| 3 2
| 4
|
| 4 3
| 0
|