My brute-force algo got ac... But it runs more than 1 minute on tests like this:
50000 1 50 0.4
-25000 -25000
-24999 -24999
-24998 -24998
-24997 -24997
-24996 -24996
.......
.......
24999 24999
25000 25000

Edited by author 18.10.2007 07:07

Thank you for test. By the way, this test is incorrect, K should be 2 or more for correctness of formula for A_i. So I have modified your test a little and added it.

oh...sorry it's my mistake