"""
My leapyear calculator.
"""

def leap_year(year):
    """
    Calculates if a year is a leap year.
    """
    if (year % 400 == 0):
        return True
    elif (year % 4 == 0):
        return True
    return False

def leap_decider(start_year, end_year):
    """
    Creates a stringtelle wich years are leap years.
    """
    current_year = start_year
    result = ""

    while current_year <= end_year:
        result += str(current_year)

        if leap_year(current_year):
            result += " is a leap year"
        else:
            result += " is not a leap year"

        if (current_year < end_year):
            result += ", "
        
        current_year += 1
    
    return result