You are given a large collection of identical heavy balls and lightweight rods. When two balls are placed at the ends of one rod and interact through their mutual gravitational attraction (as is shown on the left), the compressive force in the rod is $F$ = 1N. Next, four balls and four rods are placed at the vertexes and edges of a square (as is shown on the right). What is the compressive force in each rod in the latter case?