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 PHP (7.4.4) (judge verdict: Runtime Error)

<?php
$a = (fgets(STDIN));
$b = (fgets(STDIN));
 
$c = str_split($a);
$d = str_split($b);
 
$num = strlen($a);
 
if($a == $b){
  echo 0;
  exit;
}
$count = 0;
 
for($i = 0;$i<$num;$i++){
  if($c[$i] !== $d[$i]){
    $count++;
  }
}
 echo $count;
>