def least_common_multiple(number1: int, number2: int) -> int:
    """Return least common multiple of number1 and number2."""
    start1 = number1
    start2 = number2

    while number1 != number2:
        if number1 < number2:
            number1 += start1
        elif number2 < number1:
            number2 += start2
    return number1