A = input()[::-1]
B = input()[::-1]

answer = []

for i in range(100):
    if len(A) > i and len(B) > i:
        a, b = int(A[i]), int(B[i])
        answer.append(str(a ^ b))
    elif len(A) > i:
        answer.append(A[i])
    elif len(B) > i:
        answer.append(B[i])

print(int('0b'+"".join(answer[::-1]), base=2))