Conway's 99-graph problem

Conway's 99-graph problem is a well-known problem in the field of graph theory proposed by the mathematician John Horton Conway. The problem asks whether it is possible to find a connected graph on 99 vertices in which every vertex has an even degree. In graph theory, a fundamental result is that a graph can only be Eulerian (i.e., it contains an Eulerian circuit that visits every edge exactly once) if every vertex has an even degree.