A = input()        
B = input()
C = abs(len(A)-len(B))   
if len(A) > len(B):
    for i in range(C):
        B = "0" + B     
else:
    for i in range(C):
        A = "0" + A     

ans = ""
for i in range(len(A)-1, -1, -1):
    if (A[i] == "0" and B[i] == "0") or (A[i] == "1" and B[i] == "1"):
        ans += "0"
    else:
        ans += "1"

ans = ans[::-1]
print(int(ans, 2))