fun main(arr:Array<String>) {
    val n = readLine()!!.toInt()
    val numbers = readLine()!!.split(" ").map { it.toLong() }
    val lcm = numbers.reduce { acc, l -> getLcm(acc, l) }
    val bunsi = numbers.map { lcm / it }.sum()
    println(lcm.toDouble()/bunsi)
}

fun getGcd(num1:Long, num2:Long):Long {
    if(num1 % num2 == 0L) {
        return num2
    }
    return getGcd(num2, num1%num2)
}

fun getLcm(num1:Long, num2:Long):Long {
    return num1/getGcd(num1,num2)*num2
}
