main :: IO ()                                                                                                              
main = getLine >>= \o -> getLine >>= \e -> putStrLn $ f o e                                                                
                                                                                                                           
f :: [a] -> [a] -> [a]                                                                                                     
f [] [] = []                                                                                                               
f [a] [] = [a]                                                                                                             
f (a:as) (b:bs) = a:b:(f as bs)