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 Kotlin (1.3.71) (judge verdict: Wrong Answer)

fun main(){
    val s : String = readLine().toString()
    val t : String = readLine().toString()
    val n : Int = s.length
    var a  = 0
    for(i:Int in 1..n){
            if (i<n && s.substring(i, i+1) == t.substring(i, i+1)){
            }
            else if(s.substring(i) == t.substring(i)){
            }
            else {
                a++
            }

    }
    println(a)
}