#33880: c290
raphaelchu0205@gmail.com
(?? “Raphael” ??)
s1=input()
L1=[i for i in s1]
L2=[int(L1[j]) for j in range(len(s1)) if j%2!=0]
L3=[int(L1[k]) for k in range(len(s1)) if k%2==0]
print(abs(sum(L2)-sum(L3)))