codeforces - 80 - A (hs)

A.hs

{-# OPTIONS_GHC -O2 -XNoMonomorphismRestriction #-}
{-# LANGUAGE BangPatterns #-}
{-(c) gorlum0 [at] gmail.com-}

isqrt x = truncate (sqrt $ fromIntegral x)

isPrime n
    | n`rem`2 == 0  = False
    | otherwise     = null [x | x <- [3,5.. isqrt n + 1], n`rem`x == 0]

-- n is prime here
nextPrime n
    | n == 2    = 3
    | otherwise = head [x | x <- [n+2,n+4..], isPrime x]

body :: [Int] -> [Bool]
body [] = []
body (n:m:xs) = (m == nextPrime n) : body xs

fmt True  = "YES"
fmt False = "NO"

main = do
    ws <- words `fmap` getContents
    let xs = map read ws
    mapM_ (putStrLn . fmt) (body xs)