In this puzzle, we only consider independent countries and we do not count overseas territories as actual part of a country. We say that three countries form a well-connected triple, if each two of them share a piece of common border with strictly positive length. Most of these well-connected triples furthermore meet at a point (at least theoretically).

Q: What are the eight well-connected triples that share (at least) two points common to all three countries?

  • $\begingroup$ so basically you're looking for a country that lies between 2 other countries and has no other neighbours? $\endgroup$
    – Novarg
    Commented Feb 11, 2015 at 14:29
  • $\begingroup$ @Novarg: No, not exactly. Azerbaijan consists of two disconnected parts, and between the two parts Armenia is bordering Iran. $\endgroup$
    – Gamow
    Commented Feb 11, 2015 at 14:39
  • $\begingroup$ The "correct answer" sign goes to Gamow who found the last (and hence hardest) answer. $\endgroup$
    – Alexis
    Commented Feb 12, 2015 at 13:30

2 Answers 2


Quick and easy answers:

  1. Mongolia, China, and Russia
  2. Switzerland, Austria, and Liechtenstein
  3. India, China, and Nepal
  4. India, China, and Bhutan

Three further answers found by shyos:

  1. Ukraine, Romania, and Moldova
  2. South Africa, Mozambique, and Swaziland
  3. France, Spain, and Andorra

And finally the "weirdest" solution:

  1. Armenia, Azerbaijan, and Iran

Based on wikipedia there are 7 country that are landlocked by two other countries.

Seven landlocked countries are surrounded by only two mutually bordering neighbors:

  • Andorra (between France and Spain)
  • Bhutan (between India and China)
  • Liechtenstein (one of the "doubly landlocked" countries, between Switzerland and Austria)
  • Moldova (between Ukraine and Romania)
  • Mongolia (between Russia and China)
  • Nepal (between India and China)
  • Swaziland (between South Africa and Mozambique)

To this group could be added two de facto states with no or limited international recognition:

  • South Ossetia (between Russia and Georgia)
  • Transnistria (between Ukraine and Moldova)

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