Can anyone explain this?

while True:
    print ("wanna exit? type a number that not between(1-11)range")
    side1 = input("Type 1st side: ")
    side2 = input("Type 2st side: ")
    side3 = input("Type 3rd side: ")
    a= [1,11]
    if   (side1 not in a) :
            print("You exit,goodbye! ")
            break
    else:
            a = int(side1)
            b = int(side2)
            c= int(side3)
            perimeter = (a + b +c )
            print ("The perimeter of triangle is :", perimeter )

i input a number between 1 and 10 , however it outputed "you exit...." again and again