River example from lecture

flowsto(ve,v).
flowsto(e,p).
flowsto(n,m).

flowsfrom(e,v).
flowsfrom(n,p).

-flowsfrom(X,Y) | canpaddle(Y,X).
-flowsto(X,Y) | canpaddle(X,Y).

-canpaddle(X,Y) | -canpaddle(Y,Z) | canpaddle(X,Z).

-flowsfrom(X,Y) | -flowsfrom(Y,Z) | flowsfrom(X,Z).
-flowsto(X,Y) | -flowsto(Y,Z) | flowsto(X,Z).

-flowsfrom(X,Y) | connectedw(X,Y).
-flowsto(X,Y) | connectedw(X,Y).
-connectedw(X,Y) | -connectedw(Y,Z) | connectedw(X,Z).
-connectedw(X,Y) | connectedw(Y,Z).

-canpaddle(ve,m).
%-connectedw(ve,p).