How to trim the tokens in Preprocessor directive in C?

[Vaughn]

Normally we use "##" (token pasting operator) to concatenate the tokens in preprocessor directives like:

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Code C - [expand]
1
2
3
#define SET_LOW(BIT)    PORT(BIT ## _PORT) &= ~(1<<BIT)
#define LED         PC0
#define LED_PORT        PORTC

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So my question is: Are there any method in C (especially in preprocessor directives) to extract just the letter "C" from "PC0" or trim the letter "P" and "0" (from code line 2nd) so that we could use it that letter in code line 1 to avoid the complication of Code line 3?