a->b , b->c ,c->a => (a,b,c) ??

Math is far less complicated than human psychology. If you've ever followed Seinfeld , you will notice that there is an eerie silence between them (the four friends ) when it's not all four together (except for Jerry and George , they've known each other for too long ... ). In fact the episode is fun only when all four are in their "nothingness" together. so (a,b,c,d) work well , but , usually any other combination sucks! The opposite is more glaringly seen, a->b , b->c & a->c , but (a,b,c) doesn;t seem to work !! (now how strange is that!!!).