
def submit():
    n = int(input())
    vlist = list(map(int, input().split()))
    
    # mergeを貪欲に行う
    curr_n = n
    while curr_n > 1:
        merge_indice = (0, 0)
        min_diff = float('inf')
        for i in range(curr_n):
            for j in range(i + 1, curr_n):
                # 平均した際にできるだけ価値が減らないペアを選ぶ
                diff = max(vlist[i], vlist[j]) - min(vlist[i], vlist[j])
                if min_diff > diff:
                    min_diff = diff
                    merge_indice = (i, j)
                    
        avg = (vlist[merge_indice[0]] + vlist[merge_indice[1]]) / 2
        vlist.pop(merge_indice[0])
        vlist.pop(merge_indice[1] - 1)
        vlist.append(avg)
        curr_n -= 1

    print(vlist[0])


if __name__ == "__main__":
    submit()