To finish with this puzzles row, here is an elegant one. Alberto (my flatmate) set me, and I spent some minutes until I sorted it out:
There are two cities in the desert.
The inhabitants of the first city always tell the truth.
The inhabitants of the second city always lie.
You have arrived to one of these cities, and you need to discover which city it is, because you want to know if you can drink from the well with a “fresh water” label.
Also, a detail to add: the cities are next to each other, so the people are mixed… there are people in both cities from the other city.
You are in a hurry, so you can ask only ONE question to one person to discover in which city you are!
Which one should it be?
If you want to know the solution, see first post.