The following crossword puzzle will be used to define and solve a constraint satisfaction problem $($CSP$).$

The following words need to be placed in the crossword puzzle $($above$)$:

$$ ADS

$$ AN

$$ AT

$$ BOX

$$ BUS

$$ ON

$$ OX

$$ RAIN

$$ SASH

$$ SAT

$$ SIT

$$ SORE

Words are to be placed at $1$ down, $1$ across, $2$ down, $3$ across.

Not all words need to be used $($there is place for $4$ words only$).$

Each word may be used at most once in the crossword.