S = eval(input())

T = eval(input())



if S == T:

    print((0))

else:

    ans = 0

    for i in range(len(S)):

        if S[i] != T[i]:

            ans += 1

    print(ans)
S = eval(input())

T = eval(input())



def solve(a,b):

    ans = 0

    for s,t in zip(S,T):

        if s != t:

            ans += 1

    return ans



print((solve(S,T)))
S = eval(input())
T = eval(input())
if S == T:
    print((0))
else:
    ans = 0
    for i in range(len(S)):
        if S[i] != T[i]:
            ans += 1
    print(ans)

S = eval(input())
T = eval(input())


def solve(a, b):
    ans = 0
    for s, t in zip(S, T):
        if s != t:
            ans += 1
    return ans


print((solve(S, T)))

-if S == T: -    print((0)) -else: + + +def solve(a, b): -    for i in range(len(S)): -        if S[i] != T[i]: +    for s, t in zip(S, T): +        if s != t: -    print(ans) +    return ans + + +print((solve(S, T)))