http://acm.timus.ru/problem.aspx?space=1&num=1330

1330.hs

import Control.Applicative
import Control.Monad
import Data.Array
 
readInt :: IO Int
readInt = readLn
 
readIntPair :: IO [Int]
readIntPair = parseLine <$> getLine
    where
        parseLine = (map read) . words

getAnswer prefixSums (from:to:_) = (prefixSums ! to) - (prefixSums ! (from - 1))
 
main = do
    n <- readInt
    numbers <- replicateM n readInt
    let prefixSums = listArray (0, n) (scanl (+) 0 numbers)
    m <- readInt
    queries <- replicateM m readIntPair
    mapM_ (print . getAnswer prefixSums) queries