import System.Environment
import Text.Printf

main = do
  [d] <- map read `fmap` getArgs
  printf "%f\n" (mean [1..d])

mean :: [Double] -> Double
mean xs = sum xs / fromIntegral (length xs)

{-  Collect time statistics
time Mean 2e7

-- Use GHC runtime system to collect statistics about heap usage and GC
-- ... +RTS args -RTS   passes args to the RTS
 
Mean 2e7 +RTS -sstderr


--Individual cost centers may be installed e.g. by
mean xs = {-# SCC "mean" #-} sum xs / fromIntegral (length xs)

-- Automatically generate cost centers
ghc --make Mean.hs -prof -auto-all -caf-all -fforce-recomp

-- RTS -p option generates .prof file
-- RTS -K100M increases the stacK size to 100M (needed for profiling overhead)

time Mean 1e6 +RTS -p -K100M
time Mean 2e6 +RTS -p -K100M
cat Mean.prof

-- Heap profiling -hc   sampling every -i sec
time Mean 2e6 +RTS -hc -i0.03 -p -K100M
hp2ps -c Mean.hp
gv Mean.ps

-- Allocation split by type -hy
time Mean 2e6 +RTS -hy -i0.03 -p -K100M

-- Allocation split by data constructor -hd
time Mean 2e6 +RTS -hd -i0.03 -p -K100M

-- Problem: mean traverses list twice!
-}