As per the question, all the even processes request only even resources(i.e. Ri & Ri+2)
Where as odd processes request:
odd resources(i.e. Rn-1 & Rn-1-2) when 'n' is even.
even resources (i.e. Rn-1 & Rn-1-2) when 'n' is odd.
Deadlock can only happen when even and odd processes request overlaps i.e. odd processes have to request even ...