N=input()
N=N.rstrip().split(" ")
list1=[]
list2=[]
N1=int(N[0])
N2=int(N[1])
for i in range(41):
    list1.append(N1//(2**(40-i)))
    N1=N1%(2**(40-i))
    list2.append(N2//(2**(40-i)))
    N2=N2%(2**(40-i))
#print(list1)
#print(list2)
list3=[]
for j in range(41):
    if list1[j]+list2[j]==2:
        list3.append(0)
    else:
        list3.append(list1[j]+list2[j])
ans=0
for k in range(41):
    ans=ans+list3[k]*2**(40-k)
print(ans)