The function `f(x)` takes a string input, capitalizes the first character, and rearranges any repeating characters to be placed together right after the first occurrence of the character.

[CODE]:
```python
def capital_and_group_repeats(s):
    result = ""
    s = s.capitalize()
    for letter in s:
        if letter not in result:
            repeats = s.count(letter)
            result += letter * repeats
    return result
```

Please check if this description and code accurately represent the implemented function. If there are any edge cases that I may have missed, feel free to provide more input-output pairs to test.