Iterative Sum Function

# ITERATIVE SUM FUNCTION

n = int(input("Enter the number of addends in your sum: "))


def sum_iterative(n):
    if n == 1:
        return "The answer is 1."
    elif n == 0:
        return "The answer is 0."
    elif n < 0:
        return "False argument"
    else:
        sum = 0
        for i in range(1, n + 1):
            sum += i
        return "The answer is " + str(sum) + "."


print(sum_iterative(n))