[@Invariance Of C]

My solution? 

[img]https://secure.static.tumblr.com/97c687f78ea72dd49e70bbd141a3ce16/cjvy96x/bPKnc4gfj/tumblr_static_8mj83i1hwiw4s0wggcosckgwg_640_v2.gif[/img]