module Main
where

import System.Environment

usage = "Euler sum. I need 1 Parameter \"n\"::Int to tell you the Euler sum from 1 to n"

main = do
         args <- getArgs
	 if length args < 1
	   then putStrLn usage
	   else putStrLn (show $ sumEuler (read (args !! 0)))



mapReduce :: (a -> b) -> (b -> b -> b) -> b -> [a] -> b
mapReduce mapF redF neutral list = foldl redF neutral (map mapF list)

sumEuler :: Int -> Int
sumEuler n = mapReduce phi (+) 0 [1..n]

phi :: Int -> Int
phi n = length (filter (relprime n) [1..(n-1)])

--alternative gcd in Prelude
hcf     :: Int -> Int -> Int
hcf x 0 = x
hcf x y = hcf y (rem x y)

relprime     :: Int -> Int -> Bool
relprime x y = hcf x y == 1