package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	t := make([]int64, 9)
	for i := 0; i < n; i++ {
		var x int
		Scan(&x)
		t[x]++
	}
	var ans int64
	for i := 1; i <= 8; i++ {
		p := int64(i)
		for j := 1; j <= 8; j++ {
			ans += t[i]*t[j]*p
			p *= int64(i)
		}
	}
	Println(ans)
}