Which is the 13th letter to the left of the 6th letter from the right when you write the English alphabets in backward order?

1. The English alphabet written in backward order is:
$$\text{Z, Y, X, W, V, U, T, S, R, Q, P, O, N, M, L, K, J, I, H, G, F, E, D, C, B, A}$$

2. The 6th letter from the right end (starting from A) is F.
3. Moving to the left of F means moving towards Z. The 13th letter to the left of F will be at the position:

$$6+13=19\text{th letter from the right end (A)}$$

4. The 19th letter from A in normal order is S.