Canonicalized Input Description:

Two strings \( s \) and \( t \) consisting of lowercase English letters.

### Example Input:
```
abcabab
ab
```

### Function Signature:
Write a function `f(s, t)` that takes in the input.
```python
def f(s: str, t: str):
    '''
    s: a string
    t: a string
    '''
```