def average(array):
    new_array = set(array)
    sum = 0
    l = len(new_array)
    for i in new_array:
        sum += i
    avg = sum / l
    return avg    
        

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