Problem:
Score : 200 points

Problem Statement

Given are strings S and T. Consider changing S to T by repeating the operation below. Find the minimum number of operations required to do so.

Operation: Choose one character of S and replace it with a different character.

Constraints

S and T have lengths between 1 and 2\times 10^5 (inclusive).

S and T consists of lowercase English letters.

S and T have equal lengths.

Input

Input is given from Standard Input in the following format:

S
T

Output

Print the answer.

Sample Input 1

cupofcoffee
cupofhottea

Sample Output 1

4

We can achieve the objective in four operations, such as the following:

First, replace the sixth character c with h.

Second, replace the eighth character f with t.

Third, replace the ninth character f with t.

Fourth, replace the eleventh character e with a.

Sample Input 2

abcde
bcdea

Sample Output 2

5

Sample Input 3

apple
apple

Sample Output 3

0

No operations may be needed to achieve the objective.

Solution in Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program sample
implicit none

character(len=2*10**5) :: S, T
integer :: a, i, sum, ans
character(1), allocatable :: p(:), q(:)

read(*,*) S, T
a = len_trim(S)
allocate(p(a))
allocate(q(a))

do i = 1, a
p(i)=S(i:i)
enddo

do i = 1, a
q(i)=T(i:i)
enddo

sum=0
do i =1, a
if(p(i) == q(i))then
sum = sum+1
endif
enddo 
ans = a - sum
write(*,*) ans

deallocate(p)
deallocate(q)

stop
end program sample