Reason · Hard
First letter that does not repeat
A word or short phrase is given.
Task
Write a prompt that finds the first letter that appears only once.
Output format
<letter> or NONE
- Capitals count as the same letter (A and a), but return the letter as written.
- Ignore spaces and punctuation.
Your prompt must contain {input}: it is replaced by each test case, just like the hidden tests in a hiring test.
Sample case 1
Input
swiss
Output
w
Sample case 2
Input
Aardvark
Output
d
There are 4 test cases in all; the others are like hidden tests: work out what tricky inputs they might use!