401. The Road to Tipperary. A popular bard assures us that "the road is long to Tipperary." Look at the attached map and tell us if you can find the best route there. The straight segments represent transitions from city to city. You need to get from London to Tipperary in an even number of transitions. It is not difficult to do this in 3, 5, 7, 9, or 11 transitions, but all these are odd numbers. The issue is that with an odd number of transitions, one very important sea crossing is omitted.

![](https://cdn.mathpix.com/cropped/2024_05_21_56f37ca27ac3d928838dg-134.jpg?height=534&width=543&top_left_y=938&top_left_x=765)

If you manage to achieve your goal and reach your destination in an even number of transitions, it will be because you have crossed the Irish Sea. Which segment of the journey crosses the Irish Sea?
401. The thick line on the diagram shows the route from London to Tipperary, made in 18 moves. To reach the destination in an even number of moves, it is absolutely necessary to include in the route the move marked by the words Irish Sea.

![](https://cdn.mathpix.com/cropped/2024_05_21_56f37ca27ac3d928838dg-290.jpg?height=531&width=629&top_left_y=1916&top_left_x=722)