a=input()
b=input()
if len(a)>len(b):
    n=len(a)
else:
    n=len(b)
a=a.zfill(n)
b=b.zfill(n)

for i in range(len(a))[::-1]:

    if int(a[i])==1 and int(b[i])==1:
        print(0)
        exit()
print(int('0b'+a,2)+int('0b'+b,2))