print(abs(sum(int(c)*(-1)**i for i,c in enumerate(input()))))
print(abs(sum(int(c)*(-1)**i for i,c in enumerate(input()))))
java 115
for(int i=0,b=1,c=0; c<1; System.out.print((i-=b>0?0:48)<0?-i:i)) while((c=System.in.read())!=10) i+=(b=-b)>0?-c:c;