This is a very objective question, but I'm going to say you must travel to 4 countries, 2 of which must be across an ocean, and 2 have to be to countries that speak different languages than your native language. Feel free to mix and match.
with these constraints, i wonder what the minimum travel distance required would be to meet these requirements. probably starting in indonesia or something. everythings across the ocean and there's lots of nearby linguistic diversity.