Start by naming any country that France borders. Then name any country that borders any of those countries. Then keep going until there are no more countries left to name.
Interesting. I didn't get any of the top answers. Highest up on each list I got was Andorra and Australia. Surprising that many countries I could name with female presidents, prime ministers, secretaries of state, chancellors etc do not make the list.
I was guessing random countries and I somehow got east Timor. I knew Rwanda had 63.8% because I just watched the Geography Now episode in which he mentioned that statistic.