N = int(input())
A = list(map(int,input().split()))

C = 9
dat = [0] * C
for a in A:
    dat[a] += 1
ans = 0
for i in range(1,C):
    for j in range(1,C):
        tmp = i ** j
        ans += tmp * dat[i] * dat[j]
print(ans)