diff = 0
def diff21(n):
    if n <= 21:
        diff = 21 - n
    else:
        diff = 2(21 - n)
    return diff

diff21(21)-> 0

diff21(19)-> 2

diff21(23)-> 4

def x(a):
    print("ok.")

diff = 0
def diff21(n):
    if n <= 21:
        diff = 21 - n
    else:
        diff = 2*(21 - n) #here
    return diff

diff = 0

def diff21(n):
    if n <= 21:
    diff = 21 - n
    return diff

elif n > 21:
    diff = 2 * abs(21 - n)
    return diff
else:
    print("Input not valid")