f = open('INPUT.TXT')
number = f.read().strip()
f.close()

n = len(number)
max_sum = -999999

for skip in range(n):
    s = 0
    pos = 0
    for i in range(n):
        if i != skip:
            if pos % 2 == 0:
                s = s + int(number[i])
            else:
                s = s - int(number[i])
            pos = pos + 1
    if s > max_sum:
        max_sum = s

f = open('OUTPUT.TXT', 'w')
f.write(str(max_sum))
f.close()