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.
Nice quiz! Maybe having the ratio in meters per square kilometer and not in km/km2 would be easier to realise what it really means. With a 0.00002 number, it is harder to see that DRC has 2 cm coastline per squarekilometer, which is absolutely crazy!