Problem:
Score : 100 points

Problem Statement

Snuke has a favorite restaurant.

The price of any meal served at the restaurant is 800 yen (the currency of Japan), and each time a customer orders 15 meals, the restaurant pays 200 yen back to the customer.

So far, Snuke has ordered N meals at the restaurant.
Let the amount of money Snuke has paid to the restaurant be x yen, and let the amount of money the restaurant has paid back to Snuke be y yen.
Find x-y.

Constraints

1 ≤ N ≤ 100

Input

The input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

20

Sample Output 1

15800

So far, Snuke has paid 16000 yen, and the restaurant has paid back 200 yen. Thus, the answer is 15800.

Sample Input 2

60

Sample Output 2

47200

Snuke has paid 48000 yen for 60 meals, and the restaurant has paid back 800 yen.

Solution in Ruby (2.3.3) (judge verdict: Accepted)

# すぬけくんはレストランに通うのが好きです。
# すぬけくん行きつけのレストランは何を食べても 1 食 800 円で、
# 15 食食べる毎にその場で 200 円もらえます。
# すぬけくんは今までで合計 N 食食べました。
# 今までに払った金額を x 円、レストランからもらった金額を y 円として、
# x−y を求めなさい。

# 今まで食べた回数を取得
n = gets.chomp.to_i

# 今までに払った金額を計算
x = n * 800

# 今までにレストランからもらった金額を計算
y = (n / 15) * 200

# 収支を出力
puts x - y