How is the second digram a legal mapping? (Playfair Cipher)

So this is a partly completed key I have:

_ R _ _ _
_ T _ _ _
_ _ H _ _
_ _ L _ _
_ P _ _ W


And this is my plaintext/ciphertext:

Plain: INALLCIPHERSYSTEMS
Cipher: HORMKRDXIGCTCBELKU


The resultant digraphs:

IN AL LC IP HE RS YS TE MS
HO RM KR DX IG CT CB EL KU


I'm tasked with completing the key, but I'm stumped on the second digraph pairing of AL and RM. Given that L and R are in different rows/cols, isn't it impossible to fill in the key s.t. A maps to R? We can't map it to R via shifting to the next row/col entry, and we can't use the rectangle method thing either because if we draw a rectangle from L to R, the opposite adjacent corner that would map to R is directly above L...

Am I missing something? Do you know a possible way of mapping A to R from those two digraphs?