先將輸入字串用list()轉換成串列，偵測偶數項和奇數項加總相減

s = input()

s = list(s)

for i in range(len(s)):

    s[i] = int(s[i])

a = 0

b = 0

for i in range(len(s)):

    if (i%2) != 0:

        a += s[i]

    else:

        b += s[i]

print(abs(a-b))