# Find the sum of digits of m?

Let $m$ be the number of numbers from set $\{1,2,3,\dots,2014\}$ which can be expressed as difference of the squares of two non negative integers. The sum of digits of $m$ is...

My attempt: I tried one by one that $1,2,4,5,6,7$ and so on. But it was very long and still I didn't got the right answer. Can anyone help me to solve this problem?

Hint: $x^2 - y^2 = (x+y)(x-y)$. $x+y$ and $x-y$ can be any integers that are either both odd or both even. So the only positive integers that can't be written in this way are ...