main' fileName = do
  Just problem <- parse fileName
  let env = populate problem
  Just a <- solution2assignment env <$> main'' env
  output a
main' fileName = do
  Just problem <- parse fileName
  let env = populate problem
  Just a <- solution2assignment env <$> main'' env
  output a
main' fileName = do
  Just problem <- parse fileName
  let env = populate problem
  Just a <- solution2assignment env <$> main'' env
  output a