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 Ruby (2.7.1) (judge verdict: Accepted)

S = gets.chomp              # 文字列。chompを付けないと改行文字がついてくる
T = gets.chomp              # 文字列。chompを付けないと改行文字がついてくる
S.freeze
T.freeze
s = S.split("")
t = T.split("")

len = s.length
ans = 0

for num in 0..s.length-1 do
  if s[num] != t[num] then
    ans = ans + 1
  end
end
puts ans