def main():
    n = int(input())
    *a, = map(int, input().split())
    a = [a.count(i) for i in range(9)]
    ans = 0
    for i in range(1, 9):
        for j in range(1, 9):
            ans += a[i]*a[j]*(i**j)
    print(ans)


if __name__ == '__main__':
    main()