fun pow(a: Int, b: Int): Long {
    var ret = 1L
    repeat(b) {
        ret *= a
    }
    return ret
}

fun main() {
    val n = readInt()
    val a = readInts()
    val counter = Array(9) { 0L }
    for (v in a) {
        counter[v]++
    }
    var ans = 0L
    for (b in 1..8) {
        for (e in 1..8) {
            ans += counter[b] * counter[e] * pow(b, e)
        }
    }
    println(ans)
}

fun readInt() = readln().toInt()
fun readInts() = readln().split(" ").map { it.toInt() }