# Function to calculate power
def pow(a: int, b: int):
    ret = 1
    for i in range(b):
        ret *= a
    return ret

# Main Function
def main():
    # Read number of elements
    n = int(input())
    # Read array elements
    a = list(map(int, input().split()))

    # Array to count frequencyc of each numbers
    counter = [0 for i in range(9)]
    for v in a:
        counter[v] += 1
    
    # Variable to store answer
    ans = 0

    for b in range(1, 9):
        for e in range(1, 9):
            ans += counter[b] * counter[e] * pow(b, e)

    # Print ans
    print(ans)

if __name__ == "__main__":
    main()