说明

圣诞节要到了，小知想给在外地的朋友寄一份礼物，于是来到快递公司询问价格。价格属于分段计价，如果重量不到5kg，则需要8元；如果重量不超过10kg且达到5kg，每公斤1.6元；如果重量超过10kg，每公斤1.5元。现在小知准备的礼物重量为a，请问小知需要付多少钱？（1<=a<=50）

[English]Christmas is coming, Xiao Zhi wants to send a gift to a friend in the field, so he came to the courier company to ask the price. The price is segmented, if the weight is less than 5kg, it costs 8 yuan; if the weight is not more than 10kg and reaches 5kg, it costs 1.6 yuan per kilogram; if the weight is more than 10kg, it costs 1.5 yuan per kilogram. Now the weight of the gift prepared by Xiao Zhi is a. How much does Xiao Zhi need to pay? (1<=a<=50)

输入格式

一个整数a，表示小知礼物的重量

 [English]An integer a, representing the weight of Xiao Zhi's gift

输出格式

小知需要付的快递费用，保留一位小数

[English] The cost of the delivery that Xiao Zhi needs to pay, keeping one decimal

<o:p></o:p>

样例

15

22.5