mod = 998244353


def main():
    import sys
    from collections import Counter
    input = sys.stdin.readline
    
    N = int(input())
    A = list(map(int, input().split()))
    
    C = Counter(A)
    ans = 0
    for a in A:
        for b in C:
            ans += (a ** b) * C[b]
    print(ans)


if __name__ == '__main__':
    main()