note Eliya <blockquote> <i> but it doesn't take into account the positions in column 1 </i> </blockquote> <p> Sorry, I'm still not sure what you want (and it's a little diffficult to infer it from code which - as you state - doesn't work). </p> <p> Are you saying the positions in column 1 are meant to represent indices in some sparse array, with all unspecified positions (such as 12498249..12512574, etc.) implicitly having a value of zero, or what? </p> <p> I think it would help if you could come up with some simplified (but sufficient/complete) sample input (say using a window size of 3) together with the desired output values. </p> 971993 972042