def average(array):
    # your code goes here
    distinct_height = set(array)
    sum_of_arr = sum(distinct_height)
    avg = sum_of_arr / len(distinct_height)
    return avg

if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    result = average(arr)
    print(result)