... 't be in 5 or 6, because we need at least ... . This leaves us with either 1 or 3. There MUST be ... an N in either 1 or 3 because you couldn ... an N in 5 and 6, but there doesn't have ... it's really saying it /1--->3, that is, if ... is an N in neither 1 nor 3, so this is ...