The program for the implementation of encoding and decoding the entered text according to the correspondence table ...?

Question

Pascal

Write a program to implement the encoding and decoding of the entered text according to the lookup table. The table should specify the correspondence between the letters of the Russian alphabet and any characters (one character is assigned to one letter). For example:
A -!
B - > C
- <
G - “
...
The dimension of the alphabet is 25 letters.
The program must take into account one of the rules, if the input text contains letters that are not in the input alphabet, then they must be ignored (skip), i.e. as a result of decoding, not the full text will be obtained.