Nested IF(AND)

I have the following formula that Excel is telling me has an error but I can't figure it out.

=IF(K6="","",IF(L6="","",IF(M6="","",IF(N6="",",IF(AND(O30=7,Q30=8,M15="NO"),9,IF(AND(O30=8,Q30=8),9,IF(AND(Q30=8,M15="YES"),8,IF(AND(K30=4,M30=5,O30=6,Q30=7),8,IF(AND(M30=4,O30=5,Q30=6),7,IF(AND(O30=7,Q30=7),8,IF(AND(Q30=7,L15="YES"),7,IF(Q30=5,6,IF(Q30=6,7,"")))))))))))))