Janez wants to make an $m\times n$ grid (consisting of unit squares) using equal elements of the form $\llcorner$, where each leg of an element has the unit length. No two elements can overlap. For which values of $m$ and $n$ can Janez do the task?
Source: Slovenia 1997 1st Grade P4
Tags: combinatorics
Janez wants to make an $m\times n$ grid (consisting of unit squares) using equal elements of the form $\llcorner$, where each leg of an element has the unit length. No two elements can overlap. For which values of $m$ and $n$ can Janez do the task?