Write four functions that directly mutate a list:

1. repeat(lst, n): Repeat lst n times.
2. add(lst, x): Adds x to the end of the lst.
3. remove(lst, m, n): Removes all elements between indices m and n inclusive in lst.
4. concat(lst, x): concatenates lst with x (another list).

Examples

lst = [1, 2, 3, 4]

repeat(lst, 3) ➞ [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4] 

add(lst, 1) ➞ [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1]

remove(lst, 1, 12) ➞ [1]

concat(lst, [3, 4]) ➞ [1, 3, 4]

Notes

Your functions should mutate the list directly, not make a copy.