合成数列の和 (Kotlin)

合成数列の和	https://qiita.com/advent-calendar/2018/composite-number
Python(/Ruby)	https://qiita.com/cielavenir/items/dcbd839b0c66af1bc971
Crystal	https://qiita.com/cielavenir/items/1a0dd1a94aca9935f5aa
Kuin	https://qiita.com/cielavenir/items/47fd18fc68055d990599
Swift	https://qiita.com/cielavenir/items/6cde3b20866c842dc9e2
Kotlin	https://qiita.com/cielavenir/items/f58eaa30f90781229a6d
Pascal	https://qiita.com/cielavenir/items/35c2fc54ca16b620c9c7

composite.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 main(args: Array<String>){
    val n=readLine()!!.toInt()
    var i=2
    var cnt=0
    var s=0
    while(cnt<n){
        if(!isPrime(i)){
            s+=i
            cnt+=1
        }
        i+=1
    }
    println(s)
}