def insert(x, li):
    if not len(li): return [x]
    hd, *tl = li 
    if x < hd: return [x, *li]
    return [hd, *insert(x, tl)]

def isort(li):
    if not len(li): return []
    hd, *tl = li 
    return insert(hd, isort(tl))

unsorted = [4,2,5,1,3]
sorted = isort(unsorted)
print(unsorted)
print(sorted)