Update: As a matter of fact, I did. Here's some Python code to prove it:

# Counts how many times a particular letter appears in a string.
# Very basic code, made it just to clown on the AI bubble.

appearances = int(0) # Counts how many times the selected char appears.
sentence = input("Write some shit: ")
sentence_length = len(sentence) # We need to know how long the sentence is for later
character_select = input("Select a character: ") # Your input can be as long as you wish, but only the first char will be taken

chosen_char = chr(ord(character_select[0]))

# Three-line version
for i in range (0, sentence_length):
    if chosen_char in sentence[i]:
        appearances = appearances + 1

# Two-line version (doesn't work - not sure why)
# for chosen_char in sentence:
#     appearances = appearances + 1
# (Tested using "strawberry" as sentence and "r" as character_select. Ended up getting a result of 10 ("strawberry" is 10 chars long BTW))
    
# Finally, print the fucking result
print("Your input contains "+str(appearances)+" appearances of the character ("+character_select+").")

There's probably a bug or two in this I missed, but hey, it still proves I'm more of a programmer than Sam Altman ever will be.