```python
LADDER = (("m", 10000), ("cm", 10), ("mm", 1))

def split_length(mm: int) -> str:
    if not isinstance(mm, (int, float, str,        raise ValueError("Length must be a whole number")
    if mm < 0:
        raise ValueError("Length cannot be negative")
    if mm % 1 != 0:
        raise ValueError("Length must be a whole number")

    mm = int(mm)
    result = ""
    for unit, L:
        count = mm // unit[1]
        mm %= unit[1]
        result += f"{[0]        if count > 0:
            result += " "
    return result
```