a = input()
b = input()

n, m = len(a), len(b)
if n < m:
    a, b = b, a
    n, m = m, n
a = a[::-1]
b = b[::-1]
ans = 0
for i in range(n):
    if i < m:
        aa, bb = int(a[i]), int(b[i])
        ans += ((aa + bb) % 2) * pow(2, i)
    else:
        aa = int(a[i])
        ans += aa * pow(2, i)
print(ans)