import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

n = int(input())
a = list(map(int,input().split()))
c = Counter(a)

ans = 0
for i in range(1,9):
  for j in range(1,9):
    ans += pow(i,j) * c[i] * c[j]

print(ans)