we are to write a function that takes a single parameter string, and then outputs each 4 letter permutation from the possible combinations of the string. so for example even if it is a 5 letter word you have to return all 4 letter combinations of the string. it can also only be solved iteratively so no recursion.

currently i've tried using nested for loops, so for instance

```
for i in word:
    for x in word:
        for z in word:
            for y in word:
                print(y)
            print(z)
        print(x)
    print(i)

```

However the issue i'm coming across is that firstly, i'm not sure on how I would concatenate these outputs into a single string output given that i cannot use lists or any form of sets/dictionaries/tuples etc. secondly, how exactly would i avoid duplicate strings?