fun main(args: Array<String>) {
    val t = readLine()!!.toInt()
    repeat(t) {
        println(getAns(readLine()!!.toInt()))
    }
}

fun getAns(r:Int):Double {
    val h = (r*r - (r*0.5).let { it*it }).let { Math.sqrt(it) }
    return h*(r*0.5)*3
}