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def is_positive_number(integer_str_value):

try:
    integer_str_value = int(integer_str_value)
    if int(integer_str_value) > 0:
        return True
    else:
        return False
    # ==================================
except ValueError:
    return False

def get_factorial_value(integer_value):

factorial = 1

for i in range(1, integer_value+1):

factorial = factorial * i

return factorial

def main():

user_input = 999

while user_input is not 0:

user_input = input("Input a positive number : ")

    if is_positive_number(user_input):
        integer_value = int(user_input)
        result = get_factorial_value(integer_value)
        print(result)
    elif user_input is '0':
            print("Thank  you  for using this program")
            break
    else:
        is_positive_number(user_input)
        print("Input again, Please")

if name == "main":

main()