def dash_separator(string: str) -> str:
    """
    (str) -> str
    Returns a string the separates each letter of the input string with a dash.

    >>> dash_separator('hello')
    h-e-l-l-o
    >>> Kirito
    K-i-r-i-t-o
    """
    result = ''
    i = 0
    while i < len(string) - 1:
        result = result + string[i] + '-'
        i += 1
    result += string[i]
    return result