import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
n = ni()
from collections import Counter

c = Counter(na())
ans = 0
for i in c:
    for j in c:
        ans += i ** j * c[i] * c[j]
print(ans)