Königsberg Bridge Problem

In the 17^th century, in the town of Königsberg in erstwhile Prussia (now Germany), there was a system of bridges on the river Pregel which divided into two branches, with two islands in between. There were seven bridges in all, as shown in the figure.

The townsfolk were fond of walking across the bridges, and soon it became apparent to them that it was impossible to take a walk in such a way that each bridge was crossed once and only once. This is known as the famous Königsberg Bridge problem.

Try and find out such a way to cross all the bridges once and only once, and if you think that it is impossible, then try to prove it. I will tell you the solution in one of my subsequent posts.