Given an input String, consider only the letters and return the sum of the Caesar-adjusted number values ('A'==1, 'B'==2, 'a'==1, 'b'==2) of the letter characters inside. The input String will have a variety of characters (not all letters). Treat lowercase and uppercase letters as having the same numeric value for purposes of this problem.

This is the first in a series of problems about cryptographic hash functions, which take in data of varying length and produce a smaller amount of data, often of a fixed length. A cryptographic hash can be used to determine data integrity of a message, or even to determine whether a user knows a secret such as a password without actually knowing the secret yourself. All the hash functions in these exercises are quite bad because they do not react strongly to small changes in input data, which should make them have wildly different results. For more about cryptographic hashing try the following simplified explainer, or the more complex version.

https://simple.wikipedia.org/wiki/Cryptographic_hash_function

https://en.wikipedia.org/wiki/Cryptographic_hash_function

HINT

String upper = str.toUpperCase();
char a = upper.charAt(0);
boolean isLetter = Character.isLetter(a);