It is firmly recommended that you do not use sum as the name of a variable, as that interferes with using the important sum function. That tends to lead to bugs, and confuses other people reading the code.
You should never use size() with a single parameter as one of the input parameters to the colon operator (":") because the colon operator is only defined when the parameters are scalars but size() with only a single parameter always returns a function. You should either use length() or use size() with two inputs to indicate which dimension you are taking the size of.
You are iterating over a size, but you are starting from 0 instead of 1. That is likely to lead you to either indexing at 0 or indexing out of bounds.
Your test should be
if NewCell{1,1}{k} == 0
