S = eval(input())

T = eval(input())

C = 0

for i in range(len(S)):

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

    pass

  else:

    C += 1

print(C)
def main():

    S = eval(input())

    T = eval(input())

    count = 0

    for i in range(len(S)):

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

            count+=1

    print(count)





if __name__  == '__main__':

    main()
S = eval(input())
T = eval(input())
C = 0
for i in range(len(S)):
    if S[i] == T[i]:
        pass
    else:
        C += 1
print(C)

def main():
    S = eval(input())
    T = eval(input())
    count = 0
    for i in range(len(S)):
        if S[i] != T[i]:
            count += 1
    print(count)


if __name__ == "__main__":
    main()

-S = eval(input()) -T = eval(input()) -C = 0 -for i in range(len(S)): -    if S[i] == T[i]: -        pass -    else: -        C += 1 -print(C) +def main(): +    S = eval(input()) +    T = eval(input()) +    count = 0 +    for i in range(len(S)): +        if S[i] != T[i]: +            count += 1 +    print(count) + + +if __name__ == "__main__": +    main()