count_5 st' = [ c | c <- st',c `elem` [ 5 ]]
count_7 st'' = [ c | c <- st'',c `elem` [ 7 ]]
is_ok :: String -> Bool
-- Implement code below
is_ok s = ( 2 == length ( count_5 s ) ) && ( 1 == length ( count_7 s ) )
-- This is related to IO , you don ’ t have to completed it XD
main = do
s <- getLine
putStrLn $ if is_ok s then " Yes " else " No "