package Yukicoder

/**
 * Created by hichikawa on 2015/11/11.
 */
fun main(args: Array<String>) {
    fun readLineLong() : Long {
        val str = readLine() as String
        return str.toLong()
    }

    val num = readLineLong()
    val inputStr1 = readLine() as String
    val inputStr2 = readLine() as String
    var count = 0
    for (i in  0..(num-1)) {
        if (inputStr1[i.toInt()] != inputStr2[i.toInt()]) {
            count++
        }
    }
    println(count)
}