シクシク素数列 (Kotlin)

シクシク素数列	https://qiita.com/advent-calendar/2018/4949prime-series
Crystal	https://qiita.com/cielavenir/items/4c95fdf14b7a247e51e0
Kuin	https://qiita.com/cielavenir/items/60993a2b2885690a3a4a
Swift	https://qiita.com/cielavenir/items/db4c93532a53bfa33ac2
Kotlin	https://qiita.com/cielavenir/items/f3ccdd5ebf245aba417c
Pascal	https://qiita.com/cielavenir/items/4c962db6825d9a5eb511

4949.kt

fun isqrt(n:Int):Int{
    if(n<=0)return 0
    if(n<4)return 1
    var x=0
    var y=n
    while(x!=y&&x+1!=y){x=y;y=(n/y+y)/2}
    return x
}

fun isPrime(i:Int):Boolean{
    if(i<2){
        return false
    }
    for(j in 2..isqrt(i)){
        if(i%j<1){
            return false
        }
    }
    return true
}

fun is4949(i:Int):Boolean{
    if(i<=0)return false
    if(i%10==4||i%10==9)return true
    return is4949(i/10)
}

fun main(args: Array<String>){
    val n=readLine()!!.toInt()
    var i=2
    var cnt=0
    while(cnt<n){
        if(is4949(i)&&isPrime(i)){
            print(i)
            if(cnt<n-1){
                print(",")
            }else{
                println()
            }
            cnt+=1
        }
        i+=1
    }
}