Integer

$\frac{\mathbb{N}\text{texttimes}\mathbb{N}}{\sim }$ Where, $\sim :\mathbb{N}\text{texttimes}\mathbb{N}\to \mathrm{Prop}$ is defined as,

$$(m,n)\sim (m^{\prime },n^{\prime })\text{ iff }m+n^{\prime }=m^{\prime }+n$$