The figure F is the intersection of N circles (they may have different radii). Find the maximal number of curvilinear “sides” which F can have. Curvilinear sides of F are the arcs (of the given circumferences) that constitute the boundary of F. (Their ends are the “vertices” of F - the points of intersection of given circumferences that lie on the boundary of F.)(N Brodsky) combinatoricscombinatorial geometry