Скласти алгоритм обчисленя значеня виразу типу x=a+b-a-b

python 3.8.1

n = 10

a = []

while n ! = 0:

    b = int(input('enter number 1 - 30: '))

    n -= 1

    if b < = 10:

        a.append(b)

if len(a) == 10:

    c = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6] + a[7] + a[8] + a[9]

elif len(a) == 9:

    c = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6] + a[7] + a[8]

elif len(a) == 8:

    c = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6] + a[7]

elif len(a) == 7:

    c = a[0] + a[1] + a[2] + a[3] + a[4] + a[5] + a[6]

elif len(a) == 6:

    c = a[0] + a[1] + a[2] + a[3] + a[4] + a[5]

elif len(a) == 5:

    c = a[0] + a[1] + a[2] + a[3] + a[4]

elif len(a) == 4:

    c = a[0] + a[1] + a[2] + a[3]

elif len(a) == 3:

    c = a[0] + a[1] + a[2]

elif len(a) == 2:

    c = a[0] + a[1]

elif len(a) == 1:

    c = a[0]

else:

    c = 0

print(c);

q = int(input('enter any number to quit'))