A skateboarder in flannel rides his skateboard to the top of a ramp.
A skateboarder is at mcdonalds.
One cannot be at mcdonalds and riding a skateboard to the top of a ramp simultaneously.
(x)
exists p1 x1.(exists x2.(at(x1,x2) & n_mcdonald(x2)) & n_skateboarder(x1))