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: Accepted)

import java.lang.Integer.min
import java.util.*

fun readInt(): Int = readLine()!!.toInt()
fun readInts(): List<Int> = readLine()!!.split(" ").map { it.toInt() }

fun parseInt(): Int {
    var digit = System.`in`.read()
    while(digit <= 32) {
        digit = System.`in`.read()
    }

    val negative = digit == '-'.toInt()
    if (negative) {
        digit = System.`in`.read()
    }
    var res = 0
    while (digit in '0'.toInt()..'9'.toInt()) {
        res *= 10
        res += digit - '0'.toInt()
        digit = System.`in`.read()
    }
    return if (negative) -res else res
}

fun gcd(x : Int, y : Int) : Int {
    var a = x
    var b = y
    var r = 0
    while(b > 0) {
        r = a % b
        a = b
        b = r
    }
    return a
}

fun main() {
//    val t = readLine()!!.toInt()
    val t = 1

    for(testNumber in 1..t) {
        val a = readLine()!!
        val b = readLine()!!

        var ans = 0
        for(i in 0 until a.length) {
            if(a[i] != b[i]) ++ans
        }

        println(ans)
    }
}