A = list(input())
B = list(input())
ans = 0
if len(A) - len(B) > 0:
	for i in range(len(A)-len(B)):
		B.insert(0, "0")
elif len(B) - len(A) > 0:
	for i in range(len(B)-len(A)):
		A.insert(0, "0")
for i in range(len(A)):
	if int(A[i]) + int(B[i]) != 1:
		A[i] = 0
	else:
		A[i] = 1
for i in range(len(A)-1, -1, -1):
	if A[i] == 1:
		ans += 2**(len(A)-i-1)
print(ans)