First off, sorry if this has been posted. I haven't seen it on here, and searching for this one was difficult (since "MI" and "MU" are both under 3 letters, and the search doesn't like that...). So again, I apologize if this is a duplicate.
Can you use only the following 4 rules to convert MI to MU?
1) xI --> xIU
2) Mx --> Mxx
3) xIIIy --> xUy
4) xUUy --> xy
Please note: "x" and "y" are placeholders for any string of characters. For example, MUUI would match rule 1 (x=MUU), rule 2 (x=UUI), or rule 4 (x=M, y=I)
Also note: the unidirectional nature of the rules...meaning you CANNOT go from MUU to MIIIU using rule 3...you can only go from MIIIU to MUU.
Also: Before anyone asks, you can use the rules as many or as few times as you like, but you can ONLY use those 4 rules.
Anyways, this is a classic puzzle. Hope this makes sense! Good luck!