Problem:
Score : 100 points

Problem Statement

Given an integer N not less than 3, find the sum of the interior angles of a regular polygon with N sides.

Print the answer in degrees, but do not print units.

Constraints

3 \leq N \leq 100

Input

Input is given from Standard Input in the following format:

N

Output

Print an integer representing the sum of the interior angles of a regular polygon with N sides.

Sample Input 1

3

Sample Output 1

180

The sum of the interior angles of a regular triangle is 180 degrees.

Sample Input 2

100

Sample Output 2

17640

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

-- vim: set fdm=marker : -- {{{
{-# OPTIONS_GHC -O2 #-}
{-# LANGUAGE UnboxedTuples #-}
{-# LANGUAGE BangPatterns #-}
import Control.Monad
import Control.Monad.Fix (fix)
import Data.Maybe
import Data.Array.Unboxed (Array, Ix, array, (!), range)
import qualified Data.ByteString.Char8 as BS

type Index = Int
type Value = Integer
type Data  = Array Index Value

tuplify2 (x:y:_) = (x,y)
tuplify2 _ = undefined

--Input functions with ByteString
readInt :: Num a => BS.ByteString -> a
readInt = fromIntegral . fst . fromJust . BS.readInteger
readIntTuple :: Num a => BS.ByteString -> (a, a)
readIntTuple = tuplify2 . map readInt . BS.words
readIntList :: Num a => BS.ByteString -> [a]
readIntList = map readInt . BS.words

getInt :: Num a => IO a
getInt = readInt <$> BS.getLine
getIntList :: Num a => IO [a]
getIntList = readIntList <$> BS.getLine
getIntNList n = map readIntList <$> replicateM (fromIntegral n) BS.getLine
getIntMatrix = map readIntList . BS.lines <$> BS.getContents
getIntTuple = readIntTuple <$> BS.getLine
getIntNTuples n = map readIntTuple <$> replicateM (fromIntegral n) BS.getLine
getIntTuples = map readIntTuple . BS.lines <$> BS.getContents

genArray n xs = array (0, n-1) [x | x <- zip [0..n] xs]
-- }}}

main = do
    n <- getInt
    print $ 180 * (n-2)